Question

What is the confidence interval estimate of the population mean percentage change in the price per share of stock during the first quarter? Do not round intermediate calculations. Enter negative values as negative numbers, if any.

Answer 1

Answer:

(-0.1059 ; - 0.0337)

Step-by-step explanation:

The data table is attached in the picture below:

These is a matched pair design ; which requires taking the difference of the two values for each sample :

The mean and standard deviation of the difference will be used to construct the confidence interval :

The mean of difference, dbar = Σx/n = - 0.0698

The standard deviation of difference, Sd ;

Sd = [√Σ(d - dbar)²/(n-1)] = 0.1054

n = sample size = 25

The confidence interval :

dbar ± [TCritical * Sd/√n]

Tcritical at 90% ; df = n -1 = 25 -1

Tcritical(90% , 24) = 1.1711

C.I = - 0.0698 ± (1.711 * 0.1054/√25)

C.I = - 0.0698 ± 0.0361

C.I = (-0.1059 ; - 0.0337)