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Statistics: Quartiles, Distribution

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1. Find the third quartile Q3 of the list of 24 sorted values shown below.
35 35 42 42 43 43 43 45 46 47 49 50 51 54 55 56 57 59 63 64 67 69 74 77
The third q2uartile Q3 is _____ (type an integer or a decimal.)

2. Which is relatively better: a score of 81 on a psychology test or a score of 50 on a economics test? Scores on the psychology test have a mean of 88 and a standard deviation of 9. Scores on the economics test have a mean of 61 and standard deviation of 5.
a. the psychology test score is relatively better because its z score is greater thatn the z score for the economics test score.
b. the economics test score is relatively better because its z score is greater thatn the z score for the psycholoy test score.
c. the psychology test score is relatively better because its z score is less than the z score for the economics test score.
d. the economics test score is relatively better because its z score is less than the z score for the psychology test score.

3. Identify the type of observational study (cross-sectional, retropective, or prospective) described below.
A reasearch company uses adevice to record the viewing habits of about 12,500 households, and the data collected today will be ued to determine the proportion of households tuned to a particular sports program.
Which type of observatinal stydy isdescribed in the problem statement?
a. a prospective study
b. a cross-sectional study
c. a retrospective study

a. Convert the fraction 3/10 to an equivalent percentage.
b. Convert 32.1% to an equivalent decimal
c. What is 23% of 200?
d. Convert 0.514 to an equivalent percentage.

5. The Gallup Organization contacts 1361 adult men who are 40 to 60 years of age and live in the United States and asks whether or not they had seen their family doctor within the past 6 months.
a. What is the population in the study?
b. What is the sample of the study?

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Solution Preview

1. First, line up the numbers in order (as it is already displayed). Divide the set into quarters. (Literally with a pencil.) Do this by first dividing the list in half (so with our case, a vertical line between the "50" and the "51"). Next, do the same with the right hand side and the left hand side.

You will have 3 lines when you are finished (four "quarters".) The line first from the left is Q1, then moving towards the right, Q2 will be next (this will be the first line you drew), then continuing toward the right, Q3 is next.

Here's the trick: If our line falls in between ...

Solution Summary

The solution determines the quartiles and distribution.

See Also This Related BrainMass Solution

Statistics : Distributions, Probability, Means, Quartiles and Five-Number Summary

1. The array below shows the number of days required for approval for
a random selection of small business loan applications:

56 21 38 17 15 67 45 48 60 56 22 53 37 17

50 92 39 16 59 73 17 31 28 51 74 42 31

What is the arithmetic mean for these observations? (Round the
calculation to two decimal places.)
a. 42.00
b. 42.78
c. 41.25
d. None of the above

2. Using the array in #1 above, calculate the median of the
distribution, rounding to two decimal places.
a. 42.00
b. 42.78
c. 41.25
d. None of the above

3. Using the array in question 1 above, calculate the arithmetic mean
with the single most extreme outlier removed. Round the
calculation to two decimal places.
a. 40.50
b. 40.89
c. 41.92
d. 43.85

4. The following is a five-number summary calculated from
observations of the percentage of calories that come from fat in 23
items advertised as "reduced" fat from a sample of fast food chain
restaurants. Form the box-and-whisker plot, select the phrase
below which bests describes the shape of the distribution.
| 15 | 20 | 22 | 26 | 30 |
|____ |______ |______ |_______|_______|

a. Skewed slightly to the left
b. Skewed slightly to the right
c. Symmetrical distribution
d. There is not enough information given to determine the shape

5. The following data represents the processing times required to pack
20 randomly selected computer hardware orders for mailing:

5.62 16.25 11.46 8.45 5.41 11.62 7.5 4.42 7.58 7.54

5.29 10.92 21.62 8.58 11.42 7.29 7.96 10.5 9.29 8.92

What is the third quartile?
a. 10.92
b. 11.05
c. 11.42
d. 11.46

6. What is the standard deviation of the distribution of the
observations in the array shown in question 11 above?
a. 0.894
b. 3.998
c. 4.199
d. 15.981

7. What is the coefficient of variation for the observations in the array
shown in question 11 above?
a. 39.97 %
b. 44.15%
c. 42.61%
d. 46.94 %

8. The employees of a company were surveyed on questions regarding
their educational background and marital status. Of the 600
employees, 400 had college degrees, 100 were single, and 60 were
single college graduates. The probability that an employee of the
company is married and has a college degree is:
a. 40/600
b. 340/600
c. 400/600
d. 500/600

9. An advertising executive is studying TV viewing habits of married
men and women during prime time hours. On the basis of past
viewing records, the executive has determined that during prime
time, husbands are watching TV 60% of the time that their wives
are also watching TV. When the husband is not watching TV, 30%
of the time his wife is watching TV. What is the probability that, if
the wife is watching TV, her husband is also watching TV?
a. 0.12
b. 0.24
c. 0.36
d. 0.67

10. Mothers Against Drunk Driving is a very visible group whose main
focus is to educate the public about the harm caused by drunk
drivers. A study was recently done that emphasized the problem we
all face with drinking and driving. Four hundred accidents that
occurred on a Saturday night were analyzed. Two items noted were
the number of vehicles involved and whether alcohol played a role in
the accident. The numbers are shown below:

Number of vehicles Involved
Did alcohol play a role? 1 2 3 Totals
Yes 50 100 20 170
No 25 175 30 230 1
Totals 75 275 50 400

Referring to the table above, what proportion of accidents involved
more than one vehicle?
a. 50/400
b. 75/400
c. 275/400
d. 325/400

11. Referring to the table in question 20 above, what proportion of the
non-alcohol related accidents were multiple vehicle accidents?
a. 50/170
b. 120/170
c. 205/230
d. 25/230

12. A company has 2 machines that produce widgets. An older machine
produces 23% defective widgets, while the new machine produces
only 8% defective widgets. In addition, the new machine produces 3
times as many widgets as the older machine does. What is the
probability that a randomly chosen widget produced by the company
is defective?
a. .055
b. .0775
c. .1175
d. .256

13. A survey is taken among customers of a fast-food restaurant to
determine preference for hamburger or chicken. Of 200 respondents
selected, 75 were children and 125 were adults. 120 preferred
hamburger and 80 preferred chicken. 55 of the children preferred
hamburger. What is the probability that a randomly selected
individual is an adult?
a. 0.50
b. 0.625
c. 0.75
d. None of the above

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