Multiple Testing: Flashcards
What is a two-sample t-test?
A t-test only comparing two samples
What is a one sample t-test?
When we compare a group to a specific mean or group
Name the function that would be used to compare the treatment and the control in a drug trial, using a two sample t-test:
t. test(output~treatment, data= )
- Where output is the treatment
- Where data is the data frame
Name the function used to compare the output to the mean in a one sample t-test:
t. test(mu= , data)
- Where mu is the population mean
- Where data is the data frame name
How do you perform a one or two-tailed t-test in R?
By adding the argument “alternative=greater/less” into line of code
Name the function used to compare the treatment and the control in a one-tailed two sample t-test:
t. test(output~treatment, alternative = “less”, data)
- Where data is the data frame
What is a paired sample t-test also known as?
A dependent sample t-test
When is a paired sample t-test used?
When samples are closely related to each other
What is an example of samples being closely related?
Measuring the same sample or patient twice before and after a certain treatment
What kind of t-test would you use when comparing cells treated with a drug versus with the control?
t-test
What kind of t-test would you use when comparing students’ grades in a BMB module of the different academic years?
t-test
What t-test would you use when comparing students’ grades before and after tutoring?
Paired t-test
What t-test would you use when comparing heights of males in Denmark versus in Tailand?
t-test
What kind of t-test would you use when measuring patients’ blood pressure before and after taking a new drug?
Paired t-test
What t-test would you use to compare the times runners take to finish a marathon before and after nutritional changes?
Paired t-test
How do you carry out a paired t-test in R?
By adding the argument “paired = True/T” to the t.test() function
List the function that would be used to compare the treatment and the control in a two tailed, two sample paired t-test:
t. test(output~treatment, paired = T, data= )
- Where data is the dataframe
What is the student t-test?
A hypothesis test
Why is it important to check the assumptions of a hypothesis test?
- They are based on certain assumptions about the data
- If data doesn’t fit with assumptions, the probability calculations underlying the test are likely to be incorrect
- This increases the chances of a false negative or false positive result
- This can have bad consequences
List the assumptions of the t-test:
- Dependent variable must be continuous and the independent variable must be bivariate
- Population (not sample) must be normally distributed
- The data of the two populations from which sample is taken must have equal variance
What does it mean that the dependent variable must be continuous?
The dependent variable is the outcome, which needs to be continuous (able to take on any value)
What does it mean that the independent variable must be bivariate?
- The t-test can only compare two groups
- So there can only be two levels for the dependent variable
- Underlying data could have more than 2 levels but only two at a time is analysed with the t-test
What does it indicate if a sample is normal distributed?
That the population is also normally distributed
What does a normal distribution look like?
- Most values are clustered around the mean
- The tails on either side are fairly symmetrical