Questions

Question 1

What does the significance level refer to?

Answer 1

• The probability of rejecting the null hypothesis when in fact it is true.

Question 2

Why did bla bla choose a random sample?

Answer 2

• Enables proper inference about the population to be undertaken

Question 3

Explain why some of the frequencies have been combined into bigger categories

Answer 3

• If they were not combined, some of the expected frequencies would be too small (below 5) and the test statistic would be invalid

Question 4

Why would PMCC not be appropriate?

Answer 4

• Scatter diagram not elliptical
• Underlying distribution probably not bivariate normal
• The test is only valid for random on random

Question 5

What is the advantage of using a larger sample size?

Answer 5

• As sample size increases, random variation decreases
• The sample coefficient gets closer to the population correlation coefficient

Question 6

Comment on the goodness of fit of a regression line

Answer 6

• consider the r^2 value
• see if the points lie fairly close to a straight line

Question 7

Give characteristics of a random sample (other than randomness)

Answer 7

-unbiased
- representative of the population
- chosen so that the components are selected independently

Question 8

Explain why random samples are used PMCC tests

Answer 8

• a random sample allows proper inference about the population to be taken
• a random sample is unbiased