STA 200 Chapter 8 Homework
1) Using Table 8.1, a computer, or a calculator, determine the percentage of the
population falling below each of the following standard scores:
a. -1.00
b. 1.96
c. 0.84
3) Using Table 8.1, a computer, or a calculator, determine the standard score that has the
following percentage of the population below it:
a. 25%
b. 75%
c. 45%
d. 98%
4) Using Table 8.1, a computer, or a calculator, determine the standard score that has the
following percentage of the population above it:
a. 2%
b. 50%
c. 75%
d. 10%
5) Using Table 8.1, a computer, or a calculator, determine the percentage of the
population falling between the two standard scores given:
a. -1.00 and 1.00
b. -1.28 and 1.75
c. 0.0 and 1.00
6) The 84th percentile for the Stanford-Binet IQ test is 116. (Recall that the mean is 100
and the standard deviation is 16.)
a. Verify that this is true by computing the standardized score and using Table
8.1.
b. Draw picture of the original and standardized scores to illustrate this situation,
similar to the pictures in Figure 8.3.
8) Find the percentile for the observed value in the following situations:
a. GRE score of 450 (mean = 497, s.d. =115)
b. Stanford-Binet IQ score of 92 (mean = 100, s.d. = 16)
c. Woman’s height of 68 inches (mean = 65 inches, s.d. = 2.5 inches)
14) A graduate school program in English will admit only students with GRE verbal
ability scores in the top 30%. What is the lowest GRE score they will accept? (Recall
the mean is 497 and the standard deviation is 115.)
15) Use the Empirical Rule to specify the ranges into which 68%, 95%, and 99.7% of
Stanford-Binet IQ scores fall. (Recall the mean is 100 and the standard deviation is
16.)
16) For every 100 births in the United States, the number of boys follows, approximately,
a normal curve with mean of 51 boys and standard deviation of 5 boys. If the next
100 births in your local hospital resulted in 36 boys (and thus 64 girls), would that be
unusual? Explain.