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Chapter 4: Q AP1.13. (page 278)

The frequency table below summarizes the times

in the last month that patients at the emergency room of a

small-city hospital waited to receive medical attention.

Which of the following represents possible values for the median and mean waiting times for the emergency room last month?

(a) median = 27 minutes and mean = 24 minutes

(b) median = 28 minutes and mean = 30 minutes

(c) median = 31 minutes and mean = 35 minutes

(d) median = 35 minutes and mean = 39 minutes

(e) median = 45 minutes and mean = 46 minutes

Short Answer

Expert verified

The correct option is (b).

Step by step solution

01

Given information

The figure is :

Waiting timeFrequency
Less than 10 minutes5
At least 10 but less than 20 minutes24
At least 20 but less than 30 minutes
45
At least 30 but less than 40 minutes
38
At least 40 but less than 50 minutes
19
At least 50 but less than 60 minutes
7
At least 60 but less than 70 minutes
2
02

Concept

A simple random sample (SRS) of size n is made up of n people chosen from the population with an equal chance of being the sample that is actually chosen.

03

Calculation

The frequency table below highlights the times that patients in a small-city hospital's emergency room waited for medical attention in the previous month:

Class intervalxfc.f.f.x.
<10
55525
10-20152429360
20-302545741125
30-4035381121330
40-504519131855
50-60557138385
60-70652140130
Total
N=140
4210





Mean=∑i=1nfixi∑i=1nfi=4210140=30.071=30minutes

Median=l+h2(N2-c)=20+10451402-29=29.11=29minutes

Hence the correct option is (b).

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Most popular questions from this chapter

Systematic random sample Sample surveys often use a systematic random sample to choose a sample of apartments in a large building or housing units in a block at the last stage of a multistage sample. Here is a description of how to choose a systematic random sample. Suppose that we must choose 4 addresses out of 100 Because 100/4=25 we can think of the list as four lists of 25 addresses. Choose 1 of the first 25 addresses at random using Table D. The sample contains this address and the addresses 25,50, and 75 places down the list from it. If the table gives 13, for example, then the systematic random sample consists of the addresses numbered 13,38,63, and 88

(a) Use Table D to choose a systematic random sample of 5 addresses from a list of 200 Enter the table at line 120

(b) Like an SRS, a systematic random sample gives all individuals the same chance to be chosen. Explain why this is true. Then explain carefully why a systematic sample is not an SRS.

Effects of binge drinking A common definition of “binge drinking” is 5 or more drinks at one sitting for men and 4 or more for women. An observational study

finds that students who binge drink have lower average GPA than those who don’t. Identify a lurking variable that may be confounded with the effects of binge drinking. Explain how confounding might occur.

Improving response rate How can we reduce the rate of refusals in telephone surveys? Most people who answer at all listen to the interviewer’s introductory remarks and then decide whether to continue. One study made telephone calls to randomly selected households to ask for opinions about the next election. In some calls, the interviewer gave her name, in others she identified the university she was representing, and in still others, she identified both herself and the university. For each type of call, the interviewer either did or did not offer to send a copy of the final survey results to the person interviewed. Do these differences in the introduction affect whether the interview is completed?

Each of the following is a source of error in a sample survey. Label each as sampling error or non sampling error, and explain your answers.

(a) The telephone directory is used as a sampling frame.

(b) The person cannot be contacted in five calls.

(c) Interviewers choose people walking by on the sidewalk to interview.

2. A survey paid for by makers of disposable diapers found that 84% of the sample opposed banning disposable diapers. Here is the actual question:

When we take a census, we attempt to collect data from

(a) a stratified random sample.

(b) every individual selected in an SRS.

(c) every individual in the population.

(d) a voluntary response sample.

(e) a convenience sample.
See all solutions

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