Design Lab
What is the difference between a positive and negative control?
Positive control is expected to show a known effect, and the negative control is expected to show no effect.
Which variable belongs on the X-axis and the Y-axis, respectively?
Independent variable on the X, and dependent variable on the Y.
What is the minimum number of peer-reviewed sources students are required to cite in their lab report?
At least 2
A student investigates whether light affects isopod behavior. The illuminated side of the chamber is also warmer than the dark side. What's the problem?
Temperature is a confounding variable. Any observed preference could result from light, temperature, or both.
What organism is primarily studied in the behavioral experiments in BIO 204?
Isopods
What is the difference between the independent variable and the dependent variable?
The independent variable is manipulated, and the dependent variable is what is measured.
What is the chi-square formula?
χ² = Σ [(O − E)² / E]
What section of a primary research article would most likely contain this passage? "Isopods are suitable model organisms for investigating the effects of changing climatic variables on aggregation behavior. However, to our knowledge, no study has determined how aggregation behavior of different species of terrestrial isopods with variable degrees of…"
Introduction/Discussion
A student wants to determine if temperature affects isopod activity. They measure how far the isopods travel but never define what qualifies as movement. How should they improve the design?
Clearly operationalize activity, such as distance traveled in centimeters over two minutes, with a standardized measurement method.
What is the difference between a research hypothesis and a null hypothesis?
A research hypothesis proposes an explanation, and a null hypothesis states that there is no difference, effect, or preference.
What is the difference between a hypothesis and a prediction?
A hypothesis is a proposed explanation, and a prediction is something that describes an expected result, assuming the hypothesis is correct.
What is the difference between R vs. R^2?
R: The correlation coefficient describes the relationship between two variables. The R value can be between 0 (no correlation) and 1 (perfect positive correlation) or -1 (perfect negative correlation). The positive or negative refers to the type of relationship between the 2 variables. Remember: A high correlation suggests a relationship between two variables, but does not determine the cause-and-effect relationship.
R2: The coefficient of determination is an indication of how well the trendline mathematically describes the data, with a perfect match being 1 and no match being 0. R2 can only be positive.
The Introduction is worth 20 points, split between background/purpose/rationale and the hypothesis with predictions. This is how many points go to the hypothesis and predictions
4 points
A student would like to test whether isopods prefer light or dark environments. They put 10 isopods into a choice chamber and record their locations only once, immediately after they are released. What is wrong with this design?
The isopods were not given enough time to acclimate and explore the chamber. In the future, allow a habituation period and record observations at several time intervals throughout the experiment.
What is the purpose of the Materials and Methods section of the lab report?
To describe the experiment in enough detail that another person can replicate the experiment.
A student is testing whether temperature affects the movement of isopods, but also changes the light intensity between the groups. What is wrong with this experiment, and why?
The light intensity is a confounding variable since it could also affect the movement of the isopods; this should be kept constant.
What are the 5 criterias for t-test?
Data are Continuous, 5 or more data sets per group (> 5), Independent samples, Representative, random samples, Data are normally distributed
What % of figure/table points are descriptive captions?
25%
A student tests whether moisture affects how active isopods are. They run 6 trials with a damp paper towel on the bottom of a dish, all in the morning, then 6 trials with a dry paper towel in the same dish, all in the afternoon. Between trials, they only wipe the dish with a dry paper towel. Isopods are more active in the morning trials, so the student concludes that moisture increases activity. Identify 1 weakness and explain how to improve them.
1. Confounding with time of day; randomize or alternate the order of conditions throughout the day.
2. Residual cues in the dish; clean the dish thoroughly between trials or use a fresh dish each time.
Two equally sized isopod trials produce opposite habitat preferences. Why could combining these results into a single data set be misleading?
The opposite preference can cancel one another out, hiding the differences seen each trial and making the results misleading.
An experiment concludes that isopods prefer wet sponges over dry sponges. How could you design a follow-up experiment to ensure that moisture, instead of light, is causing this preference
Provide wet and dry environments under the same light conditions, keeping all other variables constant, and compare the behavior of the isopods across several trials.
Describe at least 5 changes to a graph to make it Knisley format.
1. No border surrounding the graph
2. Axes with lines or tick marks
3. Axes with titles and/or units
4. Line or scatter plots displaying more than 1 variable use different marker shape/color
5. No gridlines
6. A descriptive figure and caption
What are the 5 key components in discussions that a student should include in their lab report?
Critically interprets key findings
Integrates data from peer-reviewed sources to support their findings
Discusses uncertainty
Presents design flaws and bias
Summarizes all findings and presents potential future experiments
A student wants to investigate whether isopods prefer humid environments. They place five isopods into a choice chamber with a wet paper towel on the left and a dry paper towel on the right. They record the number of isopods on each side after 30 seconds. They repeat the experiment 10 times with the same five isopods, always keeping the wet towel on the left. They conclude that isopods strongly prefer humid environments because 80% of their observations showed more isopods on the wet side. Identify at least three potential weaknesses in this experimental design and explain how to improve them.
Positional bias: The wet side is always on the left. Randomize or alternate sides.
Pseudoreplication: Reusing the same five isopods does not create 50 independent animals.
Insufficient observation period: Thirty seconds may not allow adequate exploration or acclimation.
How many pairs of legs does an adult terrestrial isopod have?
7 pairs (14 individual legs)