Question

Suppose the scores on an exam are normally distributed with a mean μ = 75 points, and standard deviation σ = 8 points. The instructor wanted to "pass" anyone who scored above 69. What proportion of exams will have passing scores?

(a) .25 (b) .75 (c) .2266 (d) .7734 (e) -.75

Answer 1

(d): 0.7734

Explanation:

Using the normcdf( statistical function built into my old TI 83-Plus calculator, I find that the area under the standard normal curve from the extreme left to the value 69 is 0.2266. Thus, about 0.2266 of students would fail and

1.000-0.2266, or 0.7734 would pass. This corresponds to Answer (d).