Section 3.3 Solutions
3.39
a. Perhaps the adult population of the
b. The nonresponse
rate is 
.
c. The possible response error is that people
may misremember how many movies they have seen in the last year.
3.40
Label the apartment complexes 1-33 (going down the columns).
From Table B, line 117, the sample includes: 16, 32, 18, 06, 23.
Hence, Fairington,
3.53
5000 accounts receivable:
100 over $50,000
500 between $1000 - $50,000
4400 below $1000
Stratified sampling plan: sample all (i.e., 100) accounts over $50,000, sample 5% (i.e., 25) of the accounts between $1000 and $50,000, sample 1% (i.e., 44) of the accounts below $1000.
Label the midsize accounts 1-500. Beginning at line 115 in Table B, the following numbers constitute the first 5 accounts in the sample: 417, 494, 322, 247, and 097.
Label the small accounts 1-4400. Beginning at line 116 in Table B, the following numbers constitute the first 5 accounts in the sample: 1445, 4248, 0371, 3622, and 1181.
3.56
a. The sample size is 4316 + 8986 + 1182 = 14,484 people.
b. This is a voluntary response sample. People who feel strongly about the issue are more likely to respond (also, with Internet polls, people can typically vote more than once). We cannot be sure of the population this sample represents.
3.58
The first question probably drew 60% favoring a tax cut, whereas the second question probably drew 22%. The second question is much more specific. If people can clearly envision the new programs that might be lost due to the tax cut, they will probably be less likely to vote for the cut.
3.59
Children from larger families are overrepresented in such a sample. For example, suppose there are 100 families with children—60 families have one child and 40 have three children. Then there are a total of 180 children (an average of 1.8 per family), and two-thirds (120/180) of these children come from families with three children. Hence, in a sample (a class) of these children, about one-third would answer “one” to the teacher’s question and about two-thirds would answer “three” to the teacher’s question. This would give a sample average of 2.33 children per family (much higher than the true average of 1.8). Instead of sampling children (who over-represent larger families), families should be sampled.