Presentation on theme: "AP Statistics Section 15 C. The most common hypothesis about the slope is _________. A regression line with slope 0 is _________. That is, the mean of."— Presentation transcript:
AP Statistics Section 15 C
The most common hypothesis about the slope is _________. A regression line with slope 0 is _________. That is, the mean of y (does/does not) change when x changes. So this says that there is no true linear relationship between x and y. Put another way, says there is ___________ between x and y in the population from which we drew our data. You can use the test for zero slope to test the hypothesis of zero correlation between any two quantitative variables.
Note that testing correlation makes sense only if the observations are ______.
The test statistic is just the standardized version of the least- squares slope b. To test the hypothesis compute the t statistic Once again, we use the t-distribution with n - 2 degrees of freedom and as always our p-value is the area under the tail(s). Regressions output from statistical software usually gives t and its two-sided P-value. For a one-sided test, divide the P- value in the output by 2.
Example 15.6: The hypothesis says that crying has no straight-line relationship with IQ. The scatterplot we constructed shows that there is a relationship so it is not surprising that the computer output given on the previous page of notes give t = ______ with a two-sided P-value of _____. There is (strong/weak) evidence that IQ is correlated with crying.
Example 15.7: A previous example (3.5) looked at how well the number of beers a student drinks predicts his or her blood alcohol content (BAC). Sixteen student volunteers at Ohio State University drank a randomly assigned number of cans of beer. Thirty minutes later, a police officer measured their BAC. Here are the data. Student: Beers: BAC: Student: Beers: BAC:
Here is the Minitab output for the blood alcohol content data: The regression equation is BAC = Beers S = R-Sq = 80.0% Note: the actual calculated values are slightly different from these PredictorCoefStDevTP Constant Beers
Test the hypothesis that the number of beers has no effect on BAC. Hypotheses: The population of interest is __________________ H 0 : _______ In words, ____________________________ H 1 : _______ In words, _________________________________ where is ___________________________