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 (The Wall Street Journal, April 2, 2012). How stocks perform during the 1st quarter is an indicator of what is ahead for the stock market and the economy. Use the sample data in the file entitled Stock Prices to answer the following.

a. Let d denote the change in price per share for the company i where di=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 as changed during the 1st quarter.

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.

Company	End of 1st Quarter	Beginning of Year
Bank of New York	24.13	68.17
Kraft Foods	38.01	37.36
Dupont	52.90	45.78
Consolidated Edison	58.42	62.03
Johnson & Johnson	65.96	65.58
Union Pacific	107.48	105.94
Comcast	30.01	23.71
Applied Materials	12.45	10.71
Pfiser	43.41	41.22
General Electric	20.07	17.91
AT&T	31.23	30.24
Cisco Systems	21.15	18.08
Home Depot	50.31	42.04
JP Morgan Chase	45.98	33.25
Procter & Gamble	67.21	66.71
Verizon	38.23	40.12
Devon Energy	71.12	62.00
Lilly	40.27	41.56
Microsoft	32.26	25.96
Coco Cola	74.01	69.97
Qualcomm	68.06	54.70
Exxon Mobil	86.73	84.76
Pacific Gas & Electric	22.65	21.64
Oracle Systems	29.16	25.58
Chevron	107.21	106.40

Answer 1

a) sample mean

b)