Paper 4

Question 1

Negative correlation

Answer 1

• H0: rho = 0
• H1: rho < 0
• 5%, n=8
• critical value: 0.6125
• -0.915 < -0.6125
• sufficient evidence to reject H0
• significant evidence for a negative correlation between w and t

Question 2

Reason for correlation

Answer 2

as temperature increases, more people go outside to the beach, so less are shopping

Question 3

Regression model

Answer 3

Yes, r is close to -1

Question 4

Which variable is the explanatory variable?

Answer 4

Temperature; sales are dependent on temperature, whereas temperature is independent

Question 5

Interpret the regression equation

Answer 5

with every 1 degree rise in temperature, sale figures drop by £171

Question 6

Wind direction hypothesis test

Answer 6

1) Let X = the number of days out of 36 on which daily mean wind direction is between the bearings 135 degrees and 225 degrees
2) H0: p = 0.25
3) H1: p /=/ 0.25
4) Under H0, X is binomially distributed as (36, 0.25)
5) Reject H0 at a 10% significance level if…
6) 15 > 14