Stats Part 2 Flashcards
(27 cards)
What is a confidence interval?
A range of values that likely contains the population parameter.
What does a 95% confidence interval mean?
If we took many samples, 95% of the resulting intervals would contain the true parameter.
What affects the width of a confidence interval?
Sample size, variability, and confidence level.
How does sample size affect a confidence interval?
Larger sample sizes make the interval narrower.
What is the margin of error?
The maximum expected difference between the estimate and the true value.
What is a null hypothesis?
A statement that there is no effect or difference.
What is an alternative hypothesis?
A statement that there is an effect or difference.
What is a test statistic?
A value calculated from sample data to assess evidence against the null hypothesis.
What is a p-value?
The probability of observing data as extreme or more extreme if the null hypothesis is true.
What is the decision rule for a p-value?
Reject the null if p < alpha (e.g. 0.05).
What is a Type I error?
Rejecting the null hypothesis when it is actually true (false positive).
What is a Type II error?
Failing to reject the null hypothesis when it is false (false negative).
What is statistical power?
The probability of correctly rejecting the null hypothesis when the alternative is true.
What affects statistical power?
Sample size, effect size, variability, and significance level.
How are Type I and Type II errors related?
Reducing one usually increases the other unless sample size is increased.
What is a one-sample t-test?
A test to compare the sample mean to a known population mean.
When is a t-test used instead of a z-test?
When the population standard deviation is unknown and the sample size is small.
What are assumptions of a t-test?
Normality of data, random sampling, independent observations.
What is a two-sample t-test?
A test to compare the means of two independent groups.
What is a paired t-test?
A test to compare means from the same group at different times or under two conditions.
When do you use a Welch’s t-test?
When comparing two groups with unequal variances.
What is an effect size?
A measure of the strength or magnitude of a relationship or difference.
What is Cohen’s d?
A standardized effect size for comparing two means.
Why is effect size important?
It shows the practical significance of a result, not just statistical significance.
