# Week 6 Flashcards

What is a population?

all units of interest,(which can’t all be

measured)

What are samples?

subsets of units taken for analysis

What does sampling introduce?

sampling introduces uncertainty, because

properties of samples differ from true population values simply by chance

What is sampling error?

chance deviations of sample values from true population values are called sampling error

What is the goal of statistics?

Estimate the values of important parameters, including:

- means
- proportions
- variances
- effects

What are the steps in hypothesis testing?

- State the hypotheses
- Compute the test statistic with the data
- Determine the P-value
- Draw the appropriate conclusions

What is the null hypothesis(H0)?

is a specific statement about its value

no effect, no difference, nothing interesting going on

What is the alternate hypothesis (HA)?

covers every other possibility

some effect, some difference, something

interesting going on

if data is consistent with null hypothesis what should be done?

If data are consistent with the null hypothesis, we fail to reject it

we never say it’s accepted or true!

if data is inconsistent with null hypothesis what should be done?

If data are inconsistent with the null hypothesis, we reject it and say that the alternate hypothesis is supported instead

What are test statistics used for?

to see whether mismatch compatible with chance, or too extreme for chance to explain

When should a t test be used?

when hypotheses compare • a mean to a null value • two means • two paired means (e.g., before/after) • slopes or trends to null values

When should an F test or ANOVA be used?

more than two means

with numerical response and categorical explanatory variable

When should χ2 (chi-squared) be used?

When hypotheses compare

• frequencies or proportions to null values

• frequencies or proportions

What is the p-value?

the probability of obtaining a test statistic as extreme as we did if the null hypothesis is true