What is the Significance of Testing Population Variance in a Sample?

In summary, the conversation discusses the probability of a sample of 22 people voting for a candidate, and how it relates to the hypothesis being tested. The expected value and cumulative probability are important factors in determining the likelihood of the observed sample. The concept of p-values and significance is also mentioned, and it is noted that the author may not explicitly state it, but the idea of testing significance is always present in this type of analysis.
  • #1
gxc9800
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Homework Statement


Given that 8 person vote for Mr Tan , i can't understand why the probability is sum of 0 people vote for him until 8 people vote for him. Why not the probability = 22c8 ( (0.6)^8 )( (0.4)^14) ?

Homework Equations

The Attempt at a Solution

 

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  • #2
gxc9800 said:
Why not the probability = 22c8 ( (0.6)^8 )( (0.4)^14) ?
The probability ##22c8 ( (0.6)^8 )( (0.4)^14)## is the likelihood of drawing exactly this sample assuming the claim is true. When testing the hypothesis, you are comparing the cumulative probability of this sample (at least 8 people), against the claim.
Note that the expected value, assuming his claim is true would be ##22(.6)=13.2## people. If you just take the probability of 13 people saying they support him, that will not be 50%, but the cumulative probability will be close to that.
 
  • #3
hi, When testing the hypothesis, you are comparing the cumulative probability of this sample (at least 8 people), against the claim

why the author doesn't say 'the investigator selects a random smaple of 22 people and at most 8 people agree to vote for him ' instead?
 
  • #4
The question is: How likely is it to find something at least as extreme as what was observed? That is normally what people mean when they talk about p-values and significance. It is not: What is the probability of pulling this sample assuming that H0 is true?
The author may not state it, but that is what is always meant by testing significance.
 

Related to What is the Significance of Testing Population Variance in a Sample?

What is population variance and why is it important to test?

Population variance is a measure of how spread out a population's data is from its mean. It is important to test because it allows us to understand the variability within a population and make comparisons between different populations.

What is the formula for testing population variance?

The formula for testing population variance is (Σ(xi - μ)^2)/N, where Σ is the sum of the squared differences between each data point (xi) and the population mean (μ), and N is the number of data points in the population.

How do you interpret the results of a test for population variance?

The results of a test for population variance are typically presented as a single number, known as the variance. A larger variance indicates a greater spread of data points from the mean, while a smaller variance indicates a more tightly clustered set of data points.

What are some common methods for testing population variance?

Some common methods for testing population variance include the Chi-Square test, the F-test, and the Levene's test. These tests involve calculating the variance of the population and comparing it to a critical value to determine if there is a significant difference between populations.

What are some limitations of testing population variance?

One limitation of testing population variance is that it assumes the data is normally distributed, which may not always be the case. Additionally, it can be affected by outliers in the data, and may not accurately capture the variability in a population if the sample size is too small.

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