Hypothesis TestingLocked: included in All Access

How to use a sample to judge a claim about a population: the six-step process, Type I and Type II errors, power, critical values and p-values, tests of one mean, two means (independent and paired) and variances (chi-square and F), and when a nonparametric test is the better choice.

1. 1. The six steps and stating the hypothesesA hypothesis test asks whether a sample result lies so far from a claimed population value that chance alone is a poor explanation.Locked: included in All Access13 min
2. 2. Type I and Type II errors, significance and powerA test can go wrong in two ways, rejecting a true null (Type I) or missing a false one (Type II); the significance level caps the first, and power measures how well the test avoids the second.Video · 5 minLocked: included in All Access12 min
3. 3. Critical values, p-values and the decision ruleReject the null when the test statistic lands beyond the critical value or, equivalently, when the p-value is smaller than the significance level.Video · 7 minLocked: included in All Access13 min
4. 4. Testing a single meanTo test a claim about a population mean with unknown variance, measure how many standard errors the sample mean lies from the claim, using a t-statistic with n − 1 degrees of freedom.Locked: included in All Access13 min
5. 5. Two means: independent vs paired samplesBefore comparing two means, decide whether the samples are independent (pooled t-test on the difference in means) or related (paired comparisons test on the mean of the differences).Video · 6 minLocked: included in All Access14 min
6. 6. Testing variances: chi-square and FA claim about one variance is tested with chi-square; a comparison of two variances is tested with the F-ratio of the sample variances.Video · 7 minLocked: included in All Access14 min
7. 7. Parametric vs nonparametric testsParametric tests are about parameters and lean on distribution assumptions; when those assumptions fail, the data are ranks, or the question is not about a parameter, use a nonparametric test.Locked: included in All Access12 min