Table of contents
- 1. Intro to Stats and Collecting Data55m
- 2. Describing Data with Tables and Graphs1h 55m
- 3. Describing Data Numerically1h 45m
- 4. Probability2h 16m
- 5. Binomial Distribution & Discrete Random Variables2h 33m
- 6. Normal Distribution and Continuous Random Variables1h 38m
- 7. Sampling Distributions & Confidence Intervals: Mean1h 3m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 12m
- 9. Hypothesis Testing for One Sample1h 1m
- 10. Hypothesis Testing for Two Samples2h 8m
- 11. Correlation48m
- 12. Regression1h 4m
- 13. Chi-Square Tests & Goodness of Fit1h 20m
- 14. ANOVA1h 0m
3. Describing Data Numerically
Standard Deviation
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Find the standard deviation of the sample below. Round your answer to the nearest tenth.

A
24.7
B
3.9
C
607.8
D
15.5

1
Step 1: Calculate the mean (average) of the sample data. Add all the ages together and divide by the number of ages. The ages are: 24, 27, 30, 23, 20, 19, 21, 18, 25.
Step 2: Subtract the mean from each age to find the deviation of each age from the mean. This will give you a list of deviations.
Step 3: Square each deviation to eliminate negative values and emphasize larger deviations.
Step 4: Calculate the average of these squared deviations. This is known as the variance. Add all the squared deviations together and divide by the number of ages minus one (n-1) since this is a sample.
Step 5: Take the square root of the variance to find the standard deviation. This will give you the measure of spread of the ages in the sample.
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