Question

The price per share of stock for a sample of 25 companies was recorded at the beginning of 2012 and then again at the end of the 1st quarter of 2012. How stocks perform during the 1st quarter is an indicator of what is ahead for the stock market and the economy. The sample data are provided in the Excel Online file below. Construct a spreadsheet to answer the following questions.

End of 1st Quarter	Beginning of Year
26.13	18.71
39.61	34.36
54.90	43.98
60.62	59.43
67.86	62.98
108.68	104.84
31.21	21.91
13.85	9.11
44.51	39.32
21.47	15.51
33.83	29.04
23.95	16.68
51.91	40.44
47.28	30.55
69.91	64.41
40.23	38.82
73.12	60.50
41.67	39.86
33.36	24.06
75.41	68.37
70.16	51.90
89.03	83.26
25.55	18.94
31.56	23.88
108.61	104.60

a. Let  denote the change in price per share for company i where  1st quarter of 2012 price per share minus the beginning of 2012 price per share. Use the sample mean of these values to estimate the dollar amount a share of stock has changed during the 1st quarter

$  (to 2 decimals)

b. What is the 95% confidence interval estimate of the population mean change in the price per share of stock during the first quarter? Interpret this result.

Standard deviation (to 2 decimals):
Confidence interval (to 2 decimals):	(, )

The mean price per share has increase between % and % over the three-month period (to 1 decimal).

Answer 1

a) Let us denote

d = 1st quarter of 2012 price per share - the beginning of 2012 price per share

The mean price per share has increase between 5.4% and 8.9% over the three-month period