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Measures of Spread - Worksheet 10 - 9th Grade

Hard

Calculate range, IQR, and standard deviation (Hard)

27 problems · 20-25 minutes · Skills: statistics, variability, data analysis

About This Worksheet

This hard-level worksheet contains 27 problems designed for 9th Grade students practicing measures of spread. Hard worksheets feature challenging problems including multi-step questions, missing values, and real-world applications to push students further.

Spread tells you how consistent or variable a data set is — information the center alone cannot provide. Standard deviation in particular is one of the most widely used statistics in science, finance, and quality control, making it an important concept for any quantitative career.

  • Calculate range as the difference between the maximum and minimum
  • Find quartiles and compute the interquartile range (IQR)
  • Calculate and interpret standard deviation as the average distance from the mean
  • Identify outliers using the IQR rule (below Q1 minus 1.5 IQR or above Q3 plus 1.5 IQR)
  • Compare the spread of two data sets using their standard deviations

How to Solve: Worked Example

Example Problem: Find the mean and population variance of: 13, 15, 17, 19, 21
Solution Steps:
  1. Mean: (13 + 15 + 17 + 19 + 21)/5 = 85/5 = 17.
  2. Find each deviation from the mean: -4, -2, 0, 2, 4.
  3. Square them: 16, 4, 0, 4, 16, which sum to 40.
  4. Divide by the count: 40/5 = 8.
Answer: mean 17, variance 8
Tip: Squaring the deviations stops the positives and negatives cancelling to zero.
1
Find the mean and population variance: 5, 9, 13, 17, 21
2
Find the mean and population variance: 2, 5, 8, 11, 14
3
Find the mean and population variance: 2, 6, 10, 14, 18
4
Find the mean and population variance: 12, 16, 20, 24, 28
5
Find the mean and population variance: 5, 9, 13, 17, 21
6
Find the mean and population variance: 9, 12, 15, 18, 21
7
Find the mean and population variance: 15, 17, 19, 21, 23
8
Find the mean and population variance: 10, 11, 12, 13, 14
9
Find the mean and population variance: -1, 2, 5, 8, 11
10
Find the mean and population variance: 8, 11, 14, 17, 20
11
Find the mean and population variance: 12, 14, 16, 18, 20
12
Find the mean and population variance: 6, 7, 8, 9, 10
13
Find the mean and population variance: -2, 1, 4, 7, 10
14
Find the mean and population variance: 17, 18, 19, 20, 21
15
Find the mean and population variance: 7, 10, 13, 16, 19
16
Find the mean and population variance: 9, 13, 17, 21, 25
17
Find the mean and population variance: 12, 16, 20, 24, 28
18
Find the mean and population variance: 13, 15, 17, 19, 21
19
Find the mean and population variance: 11, 13, 15, 17, 19
20
Find the mean and population variance: 14, 16, 18, 20, 22
21
Find the mean and population variance: 5, 6, 7, 8, 9
22
Find the mean and population variance: 5, 9, 13, 17, 21
23
Find the mean and population variance: 6, 10, 14, 18, 22
24
Find the mean and population variance: 7, 10, 13, 16, 19
25
Find the mean and population variance: 4, 6, 8, 10, 12
26
Find the mean and population variance: 7, 11, 15, 19, 23
27
Find the mean and population variance: 11, 13, 15, 17, 19

Answer Key

1. mean 13, variance 322. mean 8, variance 183. mean 10, variance 324. mean 20, variance 325. mean 13, variance 326. mean 15, variance 187. mean 19, variance 88. mean 12, variance 29. mean 5, variance 1810. mean 14, variance 1811. mean 16, variance 812. mean 8, variance 213. mean 4, variance 1814. mean 19, variance 215. mean 13, variance 1816. mean 17, variance 3217. mean 20, variance 3218. mean 17, variance 819. mean 15, variance 820. mean 18, variance 821. mean 7, variance 222. mean 13, variance 3223. mean 14, variance 3224. mean 13, variance 1825. mean 8, variance 826. mean 15, variance 3227. mean 15, variance 8

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What skills does this statistics worksheet cover?

This worksheet focuses on statistics, variability, data analysis. It is designed for 9th Grade students and provides structured practice through varied problem types with a worked example to guide students before they begin.

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How many problems are on this worksheet?

This worksheet contains 27 problems. It typically takes 20-25 minutes to complete. An answer key with all solutions is included so parents and teachers can check work quickly.