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R2.4 Aussie, Aussie, Aussie A group of Australian students were asked to estimate the width of their classroom in feet. Use the dot plot and summary statistics below to answer the following questions.

(a) Suppose we converted each student's guess from feet to meters (3.28ft=1m). How would the shape of the distribution be affected? Find the mean, median, standard deviation, and IQR for the transformed data.

(b) The actual width of the room was 42.6feet. Suppose we calculated the error in each student's guess as follows: guess -42.6. Find the mean and standard deviation of the errors. How good were the students' guesses? Justify your answer.

Approximately locate the median (equal-areas point) and the mean (balance point) on a density curve.

Short Answer

Expert verified

a. The mean is x13.3232

The median is MEDIAN12.8049

The standard deviation is s3.8110

And the IQR is 2.5915

b. The mean is x=1.1

And the standard deviation is s=12.50.

Step by step solution

01

Part (a) Step 1: Given Information

A group of Australian students were asked to estimate the width of their classroom in feet.

Converted each student鈥檚 guess from feet to meters (3.28ft=1m)

02

Part(a) Step 2: Explanation

The following are the measurements of the classroom's width in feet:

x=43.70

localid="1649330618988" MEDIAN=42.00

s=12.50

Q1=35.50

Q3=44.00

Relationship feet - meter:

localid="1649916559499" 3.28ft=1m1ft=13.28m

The interquartile range is the area between the third and first quantiles:

localid="1649916567621" IQR=Q3-Q1=44.00-35.50=8.50

To convert these measurements from feet to meter, multiply them by 3.28:

localid="1649916575652" x=43.703.2813.3232

Let's find the median:

localid="1649916583777" MEDIAN=42.003.2812.8049

Compute the value ofs:

localid="1649916591708" s=12.503.283.8110

localid="1649916599850" IQR=8.503.282.5915

The distribution shape will not be affected because every value in the data set is translated in the same way.

03

Part(b) Step 1: Given Information

The actual width of the room was 42.6feet.

Each student's guess as:-42.6feet

04

Part (b) Step 2: Explanation

The following are the feet measurements of their classroom:

x-=43.70

s=12.50

The number of errors in the distribution is reduced by42.6percent. By the same amount, the mean is reduced:

localid="1649916610130" x=43.70-42.60=1.1

If all values decline by the same amount, the standard deviation will remain unchanged. (since the spread will not change):

s=12.50

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Most popular questions from this chapter

Jorge鈥檚 score on Exam 1in his statistics class was at the 64th percentile of the scores for all students. His score falls

(a) between the minimum and the first quartile.

(b) between the first quartile and the median.

(c) between the median and the third quartile.

(d) between the third quartile and the maximum.

(e) at the mean score for all students.

Old folks Here is a stem plot of the percent of residents aged 65 and older in the50states:

(a) Find and interpret the percentile for Colorado, which has 10.1%of its residents aged 65or older.

(b) Find and interpret the percentile for Rhode Island, with 13.9%of residents aged 65or older.

(c) Which of these two states is more unusual? Explain.

Density curves Sketch a density curve that might describe a distribution that has a single peak and is skewed to the left.

Use Table A to 铿乶d the value zfrom the standard Normal distribution that satis铿乪s each of the following conditions. In each case, sketch a standard Normal curve with your value of zmarked on the axis. Use your calculator or the Normal Curve applet to check your answers.

Working backward

(a) The 63rd percentile.

(b) 75% of all observations are greater than z.

Comparing bone density Refer to the previous exercise. One of Judy鈥檚 friends, Mary, has the bone density in her hip measured using DEXA. Mary is 35 years old. Her bone density is also reported as 948g/cm2, but her standardized score isz=0.50. The mean bone density in the hip for the reference population of 35-year-old women is 944grams/cm2.

(a) Whose bones are healthier鈥擩udy鈥檚 or Mary鈥檚? Justify your answer.

(b) Calculate the standard deviation of the bone density in Mary鈥檚 reference population. How does

this compare with your answer to Exercise 13(b)? Are you surprised?

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