Exam 13: Statistical Significance for 2 2 Tables

The first two basic steps for conducting a hypothesis test are to: 1) determine the null and alternative hypotheses 2) collect the data and summarize it with a 'test statistic.' What is the third step in the process that allows you to then make a decision?

The __________ hypothesis is usually written to express the fact that 'nothing is happening.'

Using the criterion of .05, which of the following results allows a researcher to conclude that a relationship between two categorical variables is statistically significant?

For Questions , use the following narrative Narrative: Aspirin and polyps A well-designed experiment by the Ohio State University Medical Center studied whether or not taking an aspirin a day would affect colon cancer patients' chances of getting subsequent colon polyps.In the study, 635 patients with colon cancer participated; 317 of them were randomly assigned to the aspirin group, and the other 318 patients were assigned to a placebo (non-aspirin) group.The results showed that 17% of the patients in the aspirin group developed subsequent polyps, compared to 27% of the patients in the non-aspirin group.The results are summarized in the table below. -{Aspirin and polyps narrative} Is there a statistically significant relationship between taking aspirin and developing subsequent polyps in colon cancer patients? If so, what is the relationship? Justify your answer.

A minor relationship that is found to be __________ significant is not necessarily __________ significant.

Suppose you wanted to test to see if there is a relationship between gender and driving an SUV.You take a random sample of 200 vehicles and their owners and use Minitab to analyze your data.Your computer output is below, but unfortunately the last line of the output (which would have contained the p-value) didn't print.What can you conclude? (Assume the study was conducted properly otherwise.) Expected counts are printed below observed counts SUV Non-SUV TOTAL Male 45 67 112 49)84 62.16 Female 44 44 88 39)16 48.84 Total 89 111 200 Chi-Sq = .47 + .38 + .60 + .48 = 1.92

Which of the following differences in percentages for the two categories of an explanatory variable would be considered to be statistically significant?

Suppose there is not enough evidence to conclude that the relationship in the population is real.Which of the following is not an equivalent way of saying this?

Suppose you observe a relationship between two categorical variables in a sample based on 22,000 people.If this observed relationship were based on a sample of 600 people rather than 22,000, how would this affect the believability of the results (if at all)? Explain your answer.

Suppose a researcher wanted to find out which of two chemicals works best to kill poison ivy.He conducted a controlled experiment involving 200 poison ivy plants, randomly assigned half of them to each treatment (chemical #1 or chemical #2).Five days after applying the chemicals, he recorded the data below.Is there a statistically significant relationship between type of chemical used and the results when applied to poison ivy? Conduct a hypothesis test to find out.

Whether or not we can rule out chance as an explanation for the relationship observed in a sample depends on what two things?

Is it possible for an important relationship in a population to fail to achieve statistical significance in the sample and therefore go undetected, even if the sample is selected properly and the data are collected correctly? Explain your answer.

When researchers look for a relationship between two categorical variables for individuals in the __________, they measure those categorical variables on individuals in the __________.