lab test 1 Flashcards
What are the steps of the scientific method?
✓Making observations:
- You observe a phenomenon that is in some way
interesting or puzzling.
✓ Asking questions:
- You ask a question about your observation – why? how?
✓ Formulating a hypothesis:
- You make a guess as to the explanation of the
phenomenon and derive by inductive reasoning a possible answer to the question.
✓ Making a prediction:
- You make predictions about the results you would expect if the hypothesis is correct.
✓ Testing your hypothesis:
- You devise a test to show how likely the hypothesis is valid.
✓ Analysis of your results:
- You collect and analyze the data (results) generated from the experiment that tests the hypothesis.
✓ Deriving a conclusion:
- You then interpret the results to determine whether the hypothesis is supported by the data or falsified. This leads to a conclusion
What is the independent variable?
Independent variable: Treatment or condition under study. It is the explanatory or
causal factor; the variable that you hypothesize is causing a particular response. In an
experiment, you manipulate this variable.
What is the dependent variable?
Dependent variable: Treatment or condition that is measured or observed when the
results are collected. The dependent variable is dependent on the independent variable.
The dependent variable will change in response to changes in the independent variable.
What are the controlled variables?
Controlled variables: All other factors that investigators attempt to keep the same for
all groups under study.
What is a control group?
Control Group: Group of subjects not treated with the independent variable, or which
have a natural (i.e., not manipulated) level of the independent variable.
What is an experimental group?
Experimental Group: Group of subjects treated with the independent variable, or where
the level of the independent variable is manipulated. The experimental group is also
called the treatment group.
What is the t-test used for?
Two compare the means of 2 groups
What are the 2 types of t-tests?
- Paired t-test
- Unpaired t-test
What is a paired t-test?
Comparing random samples but measures taken as a pair of observations of a single subject (comparing at one condition and then at another)
- The 2 groups need to be the same size
What is an unpaired t-test?
Comparing random samples even if the groups have different sizes
- 2 groups need to be independent, meaning they are no chances of them reacting the same way
When is the one-tail p-value used?
- When your prediction is only based on one of the groups (i.e. larger than the mean of the control group)
- When not interested in the mean difference between the groups
What are p-values for?
To evaluate the probability that the null hypothesis is correct.
- lower than 0.05= the null hypothesis is not considered
- higher than 0.05= sample is compatible with the null hypothesis
What is the null hypothesis in a t-test?
That the independent variable has no effect on the dependent variable
What does it mean when the p-value is low and when it’s high?
- When the p-value is low, the change brought by the independent is probably not due to chance
- When the p-value is high, then the effect of the dependant value on the dependent variable was probably by chance or didn’t do anything
When is the χ-square test used?
- Tests non-parametric qualitative data; most often used with count data
- Used when there is a known expected distribution that can be tested for (often in genetics)