SE of sum of 1971 sample scores = 14 x 40 = 560

SE of average of 1971 sample scores = (560/1600) x 100%

= 14/40 = 7/20 = 35/100

= .35

SE of sum of 1975 sample scores = same as 1971's = .35

(The box SD is bootstraped by the sample SD in both cases)

SE of the difference = the square root of (.35)^2 + (.35)^2

= .49

z = ( 1975 ave - 1971 ave - 0 )/ SE of difference

= (68.5 - 67.2)/.49 = 1.2/.49 = 2.6

The area under the normal curve from -2.6 to 2.6 is 99.07%, so the area to the right of 2.6 is .93/2 = .465%.

.465/100 = 4.65/1000

= 5/1000 (approx)

= 1/200