Question

A student is interested if battery life in iPhones have been negatively impacted (or improved) by updating to iOS 12. To investigate, the student collected a sample of 10 iPhones and measured battery life on the same phones before and after updating to the latest iOS version. The recorded battery life (hrs) follows:

student is interested if battery life in iPhones have been negatively impacted (or improved)

by updating to iOS 12. To investigate, the student collected a sample of 10 iPhones and

measured battery life on the same phones before and after updating to the latest iOS version.

The recorded battery life (hrs) follows:

Table 2: iPhone battery life.

iPhone \Update Before After

1 12 10

2 15 18

3 11 7

4 13 16

5 15 15

6 14 12

7 13 8

8 14 16

9 17 14

10 13 14

a. Create a third column for the table above recording the paired differences of (After −

Before).

b. Calculate the mean of the third column (this is

¯

D, the mean of paired differences).

c. Create a fourth column for the table above containing the deviations of each paired

difference to the mean of paired differences (d

i

−

¯

D).

d. Use the fourth column you created in part c to calculate the standard deviation of paired

differences, i.e. calculate sd =

s

n

P

i=1

(d

i

−

¯

D)

2

n−1

e. Finish the problem by calculating the standard error and create a 95% confide

Answer 1

a.

b.

c.

d.