Archaeology The depths (in inches) at which 10 artifacts are found are listed.
20.7 24.8 30.5 26.2 36.0 34.3 30.3 29.5 27.0 38.5
a. Find the range of the data set.
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Archaeology The depths (in inches) at which 10 artifacts are found are listed.
20.7 24.8 30.5 26.2 36.0 34.3 30.3 29.5 27.0 38.5
a. Find the range of the data set.
Pearson’s Index of Skewness The English statistician Karl Pearson (1857–1936) introduced a formula for the skewness of a distribution.
P = 3 (x̄ - median) / s
Most distributions have an index of skewness between -3 and 3. When P > 0, the data are skewed right. When P < 0, the data are skewed left. When P = 0, the data are symmetric. Calculate the coefficient of skewness for each distribution. Describe the shape of each.
a. x̄ = 17, s = 2.3, median = 19
Extending Concepts
Data Analysis Students in an experimental psychology class did research on depression as a sign of stress. A test was administered to a sample of 30 students. The scores are shown in the table at the left.
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a. Find the mean and the median of the data.
Shifting Data Sample annual salaries (in thousands of dollars) for employees at a company are listed.
40 35 49 53 38 39 40
37 49 34 38 43 47 35
a. Find the sample mean and the sample standard deviation.
Drawing a Box-and-Whisker Plot In Exercises 15–18,
(a) find the five-number summary
4 7 7 5 2 9 7 6 8 5 8 4 1 5 2 8 7 6 6 9
Extending Concepts
Alternative Formula You used SSₓ = Σ(x − x̄)² when calculating variance and standard deviation. An alternative formula that is sometimes more convenient for hand calculations is
SSₓ = Σ x² − (Σ x)² / n.
You can find the sample variance by dividing the sum of squares by n − 1 and the sample standard deviation by finding the square root of the sample variance.
b. Use the alternative formula to calculate the sample standard deviation for the data set in Exercise 15.