Anth200 SC 2 Formulas

Critical Value calculation

qt(1- 'alpha value', df = 'sample size' - 1)

Critical Value in Words

Using function qt, one minus the alpha value, and then define degrees of freedom which is the sample size minus one

How to calculate degrees of freedom

sample size minus 1

Test value in words

Sample mean minus the population mean, divided by the sample standard deviation by the square root of the sample size

Test value calculation

("xbar(or sample mean" - "population mean") / ("sample sd" / sqrt(length(primes)))

If the test value is greater than your critical value…

You reject the null hypothesis

If the test value is less than your critical value…

You fail to reject the null hypothesis

What function do you use for the critical value if you’re doing a non-directional test?

qnorm()

Critical values calculation for a non-directional test

qnorm(c (‘alpha value’, 1 - ‘alpha value’))

If your test value is greater than your positive critical value, and its less than your negative critical value, do you reject or fail to reject?

Reject

If your test value is less than your positive critical value, and its greater than your negative critical value, do you reject or fail to reject?

Fail to Reject

What critical value function do you use when you DON’T KNOW the standard deviation?

qt()

What critical value function do you use when you KNOW the standard deviation?

qnorm()

What type of test do you do if you’re comparing one individual to the population, and you know the mu and sigma?

Individual Z-Test

What type of test do you do if you’re comparing one sample to the population, and you know the mu and sigma?

One sample Z-Test

What type of test do you do if you’re comparing one sample to the population, and you know the mu and not sigma?

One sample T-Test

What type of test do you do if you’re comparing one sample before and after a certain condition?

Paired t-test

What type of test do you do if you’re comparing two seperate groups, and you don’t know mu nor sigma?

Two-sample T-test