Unit 3 Hypothesis and Z Testing

Z test assumptions

1.The population is normally distributed if the sample size is large enough to satisfy the requirements of the Central Limit Theorem

2.The population standard deviation is known (σ)

Hypothesis Testing format

•Research Problem

•Statistical Hypotheses

•Decision Rule

•Calculations

•Decision

•Interpretation

Null Hypothesis

–H₀: μ = (insert value for population mean)

–Says there is NO difference in the groups you are testing

–The sample comes from the population

–States that nothing special is happening

–Alternative Hypothesis/Research Hypothesis (H_I)

–H₁: μ ≠ (insert value for population mean)–

The idea your study is designed to test

–The sample does not come from the population

–Something special is happening

significance level

•Indicates how rare a sample mean must be to reject the null hypothesis

With α = .05 we are saying that there is a probability of .05 (p < .05) that the sample mean could have occurred by chance compared to a given population mean

Type I error•(α)

The null hypothesis is rejected when it should be retained

–The finding was actually due to chance

•Type II error (β)

The null hypothesis was retained when it should have been rejected

The finding actually was not due to chance

err on side of making type II error rather than type I