# Time to Practice Week 1

Topics: Standard deviation, Mean, Skewness Pages: 10 (1891 words) Published: October 11, 2014
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University of Phoenix Material

Time to Practice – Week One

Part A
Some questions in Part A require that you access data from Statistics for People Who (Think They) Hate Statistics. This data is available on the student website under the Student Test Resources link.

1. By hand, compute the mean, median, and mode for the following set of 40 reading scores: SUMMARY
31
32
43
42
24
34
25
44
23
43
24
36
25
41
23
28
14
21
24
17
25
23
44
21
13
26
23
32
12
26
14
42
14
31
52
12
23
42
32
34

2. Compute the means for the following set of scores saved as Ch. 2 Data Set 3 using IBM® SPSS® software. Print out a copy of the output. (Please refer to attachment)

Hospital size (number of beds)
Infection rate (per 1,000 admissions)
234
1.7
214
2.4
165
3.1
436
5.6
432
4.9
342
5.3
276
5.6
187
1.2
512
3.3
553
4.1
Mean is 335.1
Mean is 3.72

3. You are the manager of a fast food store. Part of your job is to report which special is selling best to the boss at the end of each day. Use your knowledge of descriptive statistics and write one paragraph to let the boss know what happened today. Use the following data. Do not use IBM® SPSS® software to compute the statistics needed; rather, do it by hand. Include a copy of your work. PLEASE REFER TO APPENDIX FOR WORK.

Special number
Sold
Cost
Huge Burger
20
\$2.95
Baby Burger
18
\$1.49
Chicken Littles
25
\$3.50
Porker Burger
19
\$2.95
Yummy Burger
17
\$1.99
Coney Dog
20
\$1.99
Total specials sold
119

According to the sales today, the top three items that sold the most were the Huge Burger, Coney Dog, and Chicken Littles. Based on the numbers, the store made 87.50 from the 25 chicken littles sold. In combination, the huge burger and coney dogs together made 98.80. In referencing the chart provided in the Appendix, all the items sold well, but the best-selling item is the chicken littles.

4. Suppose you are working with a data set that has some different (much larger or much smaller than the rest of the data) scores. What measure of central tendency would you use and why?

According to Salkind (2011), “The median is insensitive to extreme scores, whereas the mean is not. When you have a set of scores in which one or more scores are extreme, the median better represents the centermost value of that set of scores than any other measure of central tendency. Yes, even better than the mean (p.26).

5. For the following set of scores, compute the range, the unbiased and the biased standard deviations, and the variance. Do the exercise by hand.

31, 42, 35, 55, 54, 34, 25, 44, 35

Range = h - l = 55-25= 30
Biased SD = 10.2
Unbiased SD = 9.13
Variance = 104.04

Why is the unbiased estimate greater than the biased estimate?

The unbiased estimate is greater because the n is subtracted by 1. According to Salkind, “s (the standard deviation) is an estimate of the population standard deviation, and is an unbiased estimate at that, but only when we subtract 1 from n. By subtracting 1 from the denominator, we artificially force the standard deviation to be larger than it would be otherwise’ (p. 43).

6. Use IBM® SPSS® software to compute all the descriptive statistics for the following set of three test scores over the course of a semester. Which test had the highest average score? Which test had the smallest amount of variability? (please refer to attachment)

Test 1
Test 2
Test 3
50
50
49
48
49
47
51
51
51
46
46
55
49
48
55
48
53
45
49
49
47
49
52
45
50
48
46
50
55
53

Test 2 had the highest average score. Test 1 had the smallest amount of variability.

7. This practice problem uses the data contained in the file named Ch. 3 Data Set 3. There are two variables in this data set.

Variable
Definition
Height
Height in inches
Weight
Weight in pounds

Using IBM® SPSS® software, compute all of the measures of variability you can...

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