4. A stylist at the Hair Care Palace gathered data on the number of hair colourings given on Saturdays and on weekdays. Her results are listed below. Assume the two random samples were independently taken from normal populations.

Saturday: = 50 and = 14 Weekday: = 65 and = 13

a) (2 marks) Find the point estimate of p1 - p2.

b) (4 marks) Find a margin of error with probability .95.

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c) (5 marks) Find a 98% confidence interval for p1 - p2.

d) (2 marks) Make an interpretation of the confidence interval in c).