Exam 7: Non-Parametric Models

The _______ and _______ tests are calculated by ranking all of the scores from the two independent conditions that you are comparing from lowest to highest and adding up the ranks separately for each condition. The lowest of these summed ranks is the test statistic.

Imagine we wanted to investigate whether the reason for quitting smoking affects success rate. We recruited a sample of 120 smokers. Half wanted to quit to improve their appearance (yellow teeth and bad breath, etc.), and half wanted to quit to improve their health (life expectancy, etc.). After six months we measured how successful they had been at quitting smoking. The data were skewed so we ran a Wilcoxon rank-sum test on the data (output below). Which of the following sentences correctly reports the results from the Wilcoxon rank-sum test?

What is the Kruskal-Wallis test based upon?

A psychologist was interested in whether there was a gender difference in the use of email. She hypothesized that because women are generally better communicators than men, they would spend longer using email than their male counterparts. To test this hypothesis, the researcher sat by the computers in her research methods laboratory and when someone started using email, she noted whether they were male or female and then timed how long they spent using email (in minutes). How should she analyse the differences in males and females (use the output below to help you decide)?

What symbol represents the test statistic for the Wilcoxon signed-rank test?

Which of the following tests would you use to assess whether there is a significant difference between the mean ranks of two independent conditions?

What is the non-parametric equivalent of the independent t-test?

When the groups have equal numbers of participants in them then the test statistic (Ws) for the Wilcoxon rank-sum test is:

What is the problem with doing multiple pairwise comparisons to follow-up a significant Kruskal-Wallis test?

Non-parametric tests are used when:

You have carried out a Kruskal-Wallis test. There are significant differences between the three groups you are testing. How might you conduct your pairwise comparisons?

Imagine we wanted to investigate whether the reason for quitting smoking affects success rate. We recruited a sample of 120 smokers. Half wanted to quit to improve their appearance (yellow teeth and bad breath, etc.), and half wanted to quit to improve their health (life expectancy, etc.). After six months we measured how successful they had been at quitting smoking. The data were skewed, so we ran a Mann-Whitney test on the data (output below). Which of the following sentences correctly reports the results from the Mann-Whitney test?

A researcher measured people's physiological reactions to horror films. He split the data into two groups: males and females. The resulting data were significantly skewed and men and women had equal variances. What test should be used to analyse the data?

Which of the following non-parametric tests does not rely on the calculation of ranks?

What can be done to reduce the inflated familywise error rate that occurs when performing multiple pairwise comparisons to follow up a significant Kruskal-Wallis test?

A researcher measured people's physiological reactions while watching horror films and compared them to when watching erotic films, and a documentary about wildlife. Different people viewed each type of film. The resulting data were skewed. What test should be used to analyse the data?

When the groups have unequal numbers of participants in them then the test statistic (Ws) for the Wilcoxon rank-sum test is:

What is the parametric equivalent of the Wilcoxon signed-rank test?

What is the Jonckheere-Terpstra test used for?

The _______ test is based on calculating the difference between two sets of scores, making a note of the sign of the difference (positive or negative) and then ranking the differences from lowest to highest ignoring whether they are positive or negative.