Crafting an Effective College Lab Report: A Comprehensive Guide
The purpose of the BU lab program is to both provide a personal experience of the physical principles and also give students practice communicating their findings in a clear, concise manner with easily identifiable objectives, metrics, and results. All lab reports in the ME curriculum should be written using the same format.
Essential Components of a Lab Report
A well-structured lab report is crucial for conveying your experimental process, results, and their implications. While specific requirements may vary, a standard format ensures clarity and facilitates understanding. Note that this is a standard format but that it is not the only format possible for a lab report.
Title, Authors, and Date
Reports should be written in third person. This should include the title of the lab, course number, names of all members of the lab group, and the date on which the lab was performed. Write this as if it is going to your boss.
Abstract/Introduction
This should briefly state in your own words what you are trying to accomplish and why you are performing the experiment. DO NOT write a question. DO NOT re-write the lab handout. Give a synopsis of what you did, why you did it, and major principles you employed to do it.
Theory/Background
This section should explain the relevant theory that describes the physical principle of the lab. Equations should be properly numbered (in parentheses on the right margin), and all variables should be explained in the text. Prove you know the concepts behind what you used. Do it briefly, concisely and correctly. You must do a little reading on the topic and put things into your own words. Equations MUST BE TYPED. ALL variables must be defined.
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Materials and Methods
This should explain the measurement techniques, equipment used, and procedures to be employed in the lab. It is almost always desirable to do an analysis of some data points in the lab while the experiment is running. This is called a spot check. A spot check permits you to see if the results make sense, or if the experiment is generating data that is obviously erroneous and either the experiment or your method of analysis needs correcting. Your prelab preparation should identify the relevant equations, along with the necessary unit conversions & constants to reduce in-lab time. Then in the lab, you will only need to plug in your experimental values. DO NOT re-write the lab handout. DO NOT write a list of steps. In a technical report, you summarize what you did in prose format. You may use present or past tense, but be consistent. Give enough detail that a competent person could re-do exactly what you did and obtain the same results.
Results
This section should summarize and display the results of the experiment. This section should be purely factual, where the results are displayed primarily in the form of graphs. Describe the results clearly and concisely. Do you see expected trends? Figures should be numbered and have a caption below the figure. Use tables if appropriate. Tables should be numbered, and have a title above. Figure axes should be properly labeled, with proper units. If you have multiple trends to show, make sure to include a legend that compensates for black and white printing if you don’t have access to a color printer (ie, use distinct symbols)! Use linear or log scaling where appropriate. If you are going to comment on how two results compare then they need to be plotted on the same graph. Do not include graphs of each individual trial. Introduce and discuss all tables and figures within text - do not just throw them in.
Summarizing Findings
Use the Results section to summarize the findings of your study. The text of this section should focus on the major trends in the data you collected. In this section, just tell the reader the facts. Don't try to interpret the data or discuss why they are important.
Visual Representation of Data
One of the best ways to represent the results of your study is by using graphs and tables (in lab reports, graphs and other images are usually known as "figures"). This is because they are easy to read and convey a lot of information to the reader in an efficient way. All tables and figures should be given a number and should include a caption that explains what they are trying to convey. For example, in a paper on the effects of increased phosphorus on oxygen content of pond water, you might include a graph with this caption: "Figure 1. Any time you include a figure or table, you must mention it in the text, usually in the Results section. Add a citation in parentheses at the end of a sentence, like this: "Oxygen concentration of the pond water decreased with an increase in phosphorus (Fig. The following figure is from the bone fracture paper, showing how many men sustained bone fractures during the course of the study. Figure 1.
Discussion/Conclusion
This should examine whether the lab satisfied the stated purpose, and explain what you have observed and learned. Try to explain any differences that you observed between theory (or accepted experimental data) and experimental results. What are the implications of your results? How could they be used in the future? What different methods could you use in the future? What parameters were more important in design, less important?
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References
If you used information from external sources (ie, other than the lab manual or your own work), be sure to cite these references using appropriate bibliographic style.
Appendix
The raw data from the lab should be included in an Appendix. Sample Calculations can be included in an appendix. Data tables that are not crucial to the discussion in the lab of the results but may be helpful to the reader as a reference can be included as an appendix.
Examples of Lab Report Elements
To illustrate the principles of lab report writing, let's examine examples from different scientific contexts.
Example 1: The Effects of Jumpamine Chloride (JCl) on Jumping Performance in Frogs
This study investigates the direct effects of Jumpamine Chloride (JCl) on jumping performance in frogs of the genus Rana. Jumpamine chloride (JCl) is a natural waste product of muscle metabolism in many species of frogs (Phrogsucker et al. 1957). In addition it was reported by Phrogsucker et al. (1957) that up to 60% of this chemical is reabsorbed from the bladder before excretion. This result led to a number of studies attempting to identify the advantage of reabsorption of this product. One recent study showed that injection of JCl into the bloodstream increased muscle mass in the leopard frog Rana pipiens (Hylaflex and Smith1988). Anurheight (1990) was the first to demonstrate an actual improvement in performance capability, by showing that swimming performance in the African clawed frog Xenopus laevis was improved by adding JCl to the diet. Subsequently, in another study, tree frogs (Hyla cinerea) that had been injected with JCl were found to have measurably larger leg muscles and were able to climb higher and more quickly than those that had not (Smith 1992). The mechanism for the action of JCl on muscle growth and muscle contraction is still unknown. It may interact with enzymes involved in muscle contraction as proposed by Smith (1992) or it may directly act on the mechanical properties of the muscles themselves. This has been proposed for the action of the hormone gogetemall on muscle growth in the tree lizard Philanthropus fabricus (Herpbrain and Phutz 1992).
Hypothesis and Prediction
We hypothesized that the increased muscle mass shown in earlier studies (Hylaflex and Smith 1988) would result in improved jumping distance. We predicted, therefore, that frogs injected with JCl should have larger muscles and jump further than frogs that had not been injected with JCl. Such a result would suggest the biological function of JCl reabsorption.
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Methodology
The effects of JCl on jumping performance were tested by injecting the drug into the bloodstream of the frogs and measuring average jumping distance under specific conditions. The effects of temperature on jumping distance were evaluated by carrying out the same experiments at a range of different ambient temperatures. Ten specimens of Rana pipiens were injected with 1.0 ml. of a 10% JCl solution. Ten control frogs were given injections of 1.0 ml of a .9% NaCl solution. All frogs were maintained in 3 m square tanks at 250C for 1 day in 1 inch of water. At this time each frog was placed on an open floor and induced to jump 3 times by slapping the ground behind the frog. The jumping distance was defined as the average of the 3 jumps. Each of the JCl treated frogs was placed in a 3 m square temperature controlled tank containing 1 inch of water and ranging from 0 to 900C in intervals of 100 C. One control frog was placed in the tank with each treated frog.
Results
As shown in Table 1 the jumping distance for the control Rana pipiens was 2.3 m and for the JCl treated Rana pipiens was 4.2 m. In Rana catesbeiana the jumping distance for the control frogs was 2.6 m and for the JCl treated frogs was 2.5 m. As seen in Table 2 the greatest jumping distance of Rana pipiens was 9.0 m at 900 C and the lowest jumping distance was 2.5 m at 00 C. As seen in Table 2 for Rana catesbeiana the greatest jumping distance was 9.1 m at 900 C however the lowest jumping distance was 2.0 m at 300 C. The relationship between temperature and jumping distance is shown for Rana pipiens in Figure 2. The same relationship for Rana pipiens is shown in Figure 3. It is clear from Figure 2 that for R. pipiens jumping distance increases linearly with temperature. For R.
Discussion
JCl has the clear effect of increasing jump distance in both frog species (see Fig. 1, 2 and 3). The influence of temperature in modifying the effects of JCl on jumping performance was also evaluated. It was hypothesized that JCl acts by affecting the enzymes associated with muscle contraction. If this is the case it was predicted that jumping distance would increase exponentially with increases in temperature. Jumping distance is clearly temperature dependent. However, there are differences between the species in how this effect appears. For example, in R. catesbeiana no increase in performance occurs until the temperature exceeds 300C. This explains why no difference in jumping distance was observed at room temperature (Fig.
The nature of the relationship between temperature increase and JCl effects on jumping distance was not consistent with our original hypothesis regarding the molecular mechanism of action of JCl. We had proposed that JCl affects the activity of certain enzymes. This led us to predict an exponential increase in jumping distance with temperature. The linear increase we observed is not consistent with the proposed mechanism. It suggests that JCl may be directly acting on the mechanical properties of the muscles themselves. Such a mechanism has been proposed for the action of the hormone gogetemall in the tree lizard Philanthropus fabricus (Herpbrain and Phutz, 1992).
The observation that weight loss occurs when treated frogs are exposed to higher temperatures also suggests an effect of JCl on the overall metabolism of frogs. In Rana pipiens, reabsorption of JCl will clearly lead to increased jumping ability which can be expected to improve its survival chances. Moreover this advantage will occur at temperatures during which it is normally active (20-40 0C). The comparison with R. catesbeiana is interesting however. R. catesbeiana is not normally active above 300C. Nonetheless, R. catesbeiana absorbs JCl from its bladder. This strongly suggests that improved jumping performance alone cannot account for the evolution of the general tendency of frogs to reabsorb this substance.
The results presented here also have serious implications for the use of JCl in frog jumping contests. Twain son (1990) expressed concern that the increased occurence of doping with this drug in frog jumping contests may have dire consequences for the sport. Here we clearly show that this drug has the potential to influence the outcomes. The seriousness of the effect on the results clearly depends on the temperature at which contests are held, as well as the species involved. Moreover we have recently found that use of JCl compromises the health of our frogs.
References
Anurheigh L. 1990. The swimming abilities of frogs.Herpbrain KZ, Phutz IMA. 1992. Why do hot lizards run faster?Hylaflex JD, Smith AP. 1988. Is JCl a frog muscle builder?Phrogsucker RQ, Krabby SD, Kidding RU. 1957. Reabsorption of certain biochemicals from the frog bladder: Peeing is believing.Smith AP. 1992. JCl and climbing ability in tree frogs.Twainson CR. 1990. Frog jumping and drugs: an institution under attack.
Example 2: The Role of Color Cues in Mating Decisions of Largus californicus
This experiment investigates whether male Largus californicus bugs use color cues in their mating decisions.
Background
Adult male mating behavior suggested that the change in color from fifth instars to adults might enable males to discriminate between nymphs and adults. Ontogenetic color change at sexual maturation can be useful in identifying an appropriate mate for some organisms. Largus californicus individuals undergo two ontogenetic color changes. First instars are bright red, second through fifth instars are shiny blue-black, and adults are black with orange markings. Adult male mating behavior suggested that the change in color from fifth instars to adults might enable males to discriminate between nymphs and adults. Males mount adults and persist if they have mounted a female and quickly release if they have mounted another male. Males were never observed to mount nymphs. Female color patterns were altered and male's copulatory attempts were timed to determine if color pattern was used by males in mating decisions. Ontogenetic color change at the time of sexual maturation has been shown to be advantageous to fish (Fricke 1980), reptiles (Werner, 1978), and birds (Lyon and Montgomerie, 1986). In general, dull-colored juveniles avoid predation risk and harassment by breeding males, and sexually mature individuals use bright colors to advertise their readiness to mate (Booth, 1990a). In insects, mating cues are often chemical rather than visual (Jacobson, 1972), but there are some exceptions. In diurnal Lepidoptera, adult color pattern plays an important role in the initial phase of mating behavior (Graham et al., 1980). In holometabolous insects, such as Lepidoptera, maturation is associated with dramatic morphological changes, therefore distinguishing between larvae and adults for mating attempts is not difficult. The recognition of maturity is more difficult in hemimetabolous insects where late instars may be similar to adults in size and shape. The mating behavior of male Largus californicus suggests that males may be using visual cues, perhaps in addition to pheromonal cues, to distinguish between fifth instars and adults for mating attempts. Fifth instars are shiny blue-black and almost adult-sized. Adults (both males and females) are black with orange borders around the thickened portion of the hemelytra and pronotum (Booth, 1990b). Although males were never observed to mount nymphs, they do mount other adults, and persist if they have mounted a female or release within a few seconds if they have mounted another male. Their distinctive courtship behavior allows an observer to identify immediately the initiation of a mating event. This consists of the male orienting towards the female when he is approximately 1 cm away, rapidly waving his antennae, leaping onto the female's back, and agitatedly grabbing the female with his legs. These bugs do not fly and are easily handled and painted without significantly disrupting their normal behavior.
Methods
Experiments were designed to determine if males use color cues in their mating decision and if their behavior could explain the significance of the ontogenetic color change from fifth instars to adults. The experiment was performed outdoors at the Main Campus Reserve at the University of California, Santa Barbara on January 31, 1988. Bugs were collected from the Reserve on the morning of the testing day. An acrylic black paint and clear finish were used in each treatment. The first treatment was black paint and clear finish on the ventral surface of the female to control for the smell of the paints without altering the black and orange pattern on the dorsum. The second treatment was clear finish on the dorsum to control for covering the dorsal surface, which may reduce any scent emitted or otherwise affect the female's behavior. The third treatment was black paint on the dorsum to mimic the color of the fifth instars. One female was used for all three treatments to hold other aspects (size, shape, scent) of the female's attractiveness constant. The order of presentation of the three treatments was necessarily the same for all males, as the one female in each experiment could only have black paint added after the normal and clear treatments. After each painting, the female was placed in a clear plastic 9 x 7 x 3 cm box. Males were held separately in labeled plastic petri dishes. Each male was introduced one at a time into the box at the point farthest from the female. He was removed when he mounted the female or after an arbitrarily chosen time of 270 seconds had elapsed, whichever came first. The time to mount or 270 seconds (no-mount) was recorded. The pair was separated before their genitalia joined so no actual mating occurred. To control for the possibility of males tiring by the second or third trial, a similar number of different males were tested three times each with one untreated female; i.e. no changes were made to the female between trials. Trials were alternated between experimental and control males throughout the day of testing. Statistical analyses were performed using the StatView program on a Macintosh microcomputer.
Results
No significant differences were found in males' time to mount among the three treatments or among the three control trials based on a repeated measures ANOVA (Table 1). There was a slight, but not significant, increase in male's mean time to mount for the black treatment as compared to the normal and clear treatments (Figure 1). The 95% confidence intervals were also larger for the black treatment. The first control trial had a slightly larger, but not significantly different, male's mean time to mount as compared to the second and third trials (Figure 2).
Discussion
Because the maximal time males were allowed to stay in the box without mounting the female was chosen arbitrarily, the one case where a male did not mount the female within the allotted 270 seconds could have biased the results (Table 1). By using one female for all three color treatments, any non-color aspects of the female's attractiveness were held constant. As the null hypothesis (that males' time to mount is not significantly affected by color of the female) was not rejected, males evidently used those other traits in seeking a mate. The male behavior of mounting other adults (male or female) and not nymphs may indicate that there are pheromonal differences between nymphs and adults but not between adult males and females. Males release other males rapidly once contact has been made, so chemical cues transferred by touch or other close range signals (such as sound) may be used to distinguish males from females. There are slight shape differences between nymphs and adults (nymphs are more spherical) that could possibly be used by males in mating decisions. Among hemipterans, several species use pheromones as mating cues. Males of the southern green stink bug (Nezara viridula) release a pheromone that attracts females, males, late-stage nymphs, and a parasitoid (Aldrich et al., 1987). Females of Dysdercus cingulatus and Pyrrhocoris apterus also produce substances attractive to males (Osmani and Naidu, 1967; Zdarek, 1970). As these last two species are in the same superfamily (Pyrrhocoroidea) as L. californicus, it is possible that L. californicus females also produce a pheromone that is attractive to males. However, several species in the family Largidae, including L. cinctus (a close relative of L. californicus), have minimal development of the metathoracic scent gland evaporative area (Schaefer, 1972), so their use of pheromonal communication may be limited.
References
Aldrich, J. R., J. E. Oliver, W. R. Lusby, J. P. Kochansky and J. A. Lockwood. 1987. Pheromone strains of the cosmopolitan pest, Nezara viridula (Heteroptera: Pentatomidae). J. Exp. Zool.Booth, C. L. 1990a. Evolutionary significance of ontogenetic colour change in animals. Biol. J. Linn. Soc.Booth, C. L. 1990b. Biology of Largus californicus (Hemiptera: Largidae).Fricke, H. W. 1980. Juvenile-adult colour patterns and coexistence in the territorial coral reef fish Pomacanthus imperator. Mar. Ecol.Graham, S. M., W. B. Watt and L. F. Gall. 1980. Metabolic resource allocation vs. mating attractiveness: Adaptive pressures on the "alba" polymorphism of Colias butterflies. Proc. Natl. Acad. Sci.Jacobson, M. 1972. Insect sex pheromones.Lyon, B. E. and R. D. Montgomerie. 1986. Delayed plumage maturation in passerine birds: reliable signaling by subordinate males?Osmani, Z. and M. B. Naidu. 1967. Evidence of sex attractant in female Dysdercus cingulatus Fabr. Indian J. Exp. Biol.Schaefer, C. W. 1972. Degree of metathoracic scent-gland development in the trichophorous Heteroptera (Hemiptera). Ann. Entomol. Soc. Am.Werner, D. I. 1978. On the biology of Tropidurus delanonis, Baur (Iguanidae). Z. Tierpsychol.Zdarek, J. 1970. Mating behaviour in the bug, Pyrrhocoris apterus L. (Heteroptera): ontogeny and its environmental control.
Common Pitfalls to Avoid
- Omitting Graphics: Readers will not know the purpose of a graphic until you tell them. NEVER include a graphic without mentioning it in the text.
- Sloppiness: Sloppiness undermines the quality of the document.
- Plagiarism: As with any good thing, too much can be a problem. It can be difficult when you’ve collected information from a variety of sources to avoid representing someone else’s words or ideas as your own. Arriving at an understanding of the material which coincides with what others also understand is expected. The engineering concepts do not change over time. Expressing your understanding in your own voice with your own words though is important.
- Incomplete References: Ensure all references are complete and accurately formatted.
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