A gym owner wants to know if the gym has similar numbers of members across different age groups. The table shows the distribution of ages for members from a random survey. Find the x2 statistic to test the claim that the gym has equal numbers of members of all age ranges.
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 53m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 12m
- 9. Hypothesis Testing for One Sample2h 19m
- 10. Hypothesis Testing for Two Samples3h 22m
- 11. Correlation1h 6m
- 12. Regression1h 4m
- 13. Chi-Square Tests & Goodness of Fit1h 20m
- 14. ANOVA1h 0m
13. Chi-Square Tests & Goodness of Fit
Goodness of Fit Test
Problem 10.1.4
Textbook Question
Finding Expected Frequencies
In Exercises 3–6, find the expected frequency for the values of n and pᵢ.
n=500, pᵢ=0.9

1
Step 1: Recall the formula for expected frequency, which is given by E = n × pᵢ, where E is the expected frequency, n is the total number of trials, and pᵢ is the probability of success for a specific category.
Step 2: Identify the values provided in the problem. Here, n = 500 (total number of trials) and pᵢ = 0.9 (probability of success for the category).
Step 3: Substitute the given values into the formula. This means replacing n with 500 and pᵢ with 0.9 in the equation E = n × pᵢ.
Step 4: Perform the multiplication to calculate the expected frequency. Specifically, multiply 500 by 0.9 to find the value of E.
Step 5: Interpret the result. The expected frequency represents the number of occurrences you would expect in the category with probability pᵢ = 0.9 out of 500 trials.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Expected Frequency
Expected frequency refers to the anticipated number of occurrences of a particular outcome in a statistical experiment, calculated by multiplying the total number of trials (n) by the probability of the outcome (pᵢ). In this case, it helps in determining how many times we expect a specific event to happen based on the given probability.
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Probability
Probability is a measure of the likelihood that a particular event will occur, expressed as a number between 0 and 1. In the context of this question, pᵢ represents the probability of a specific outcome occurring in a sample of size n, which is crucial for calculating expected frequencies.
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Sample Size (n)
Sample size (n) refers to the total number of observations or trials in a statistical study. A larger sample size generally provides more reliable estimates of expected frequencies, as it reduces the impact of random variation and allows for better generalization of results to the population.
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