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15 Cards in this Set
- Front
- Back
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Define: point estimate |
The value of a simple single statistic. E.g. sample mean |
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Define: confidence interval estimate |
A range of numbers (interval) constructed around the point estimate. |
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What is the purpose of the confidence interval estimate? |
To know the probability that the population parameter is included within it. |
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Define: Sampling Error |
The error that occurs from selecting a single sample from a population |
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What is the disadvantage of increasing the confidence interval level? |
There is a trade-off between accuracy and precision: the higher the confidence interval level, the wider it is. |
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When is the confidence interval estimate inappropriate? Why? |
When the sample size and population are small enough that it does not follow a normal distribution. The confidence interval estimate uses this as a basis for calculation. |
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What are the similarity and difference between the t and normal distributions: |
Similarity: Mean = Median Difference: The normal distribution has more are in the center and less area in the tails as opposed to the t distribution. |
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How is the assumption of normality tested? |
Creating graphs: histogram, stem and leaf, boxplots, or normal probability plot and evaluating their shapes. |
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Define: critical value. |
The Z(a/2) value which is used to calculate the confidence interval. |
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What does it mean to have a 95% confidence interval. |
95% of all sample intervals contain the population mean somewhere within their corresponding intervals. |
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What is the formula to find the necessary sample size? |
n = [(Z(a/2)*sigma/e)] + 1 |
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What does x% confident mean? |
We can be x% confident that the true population parameter value is within our interval. |
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What does (n-1) degrees of freedom mean? |
(n-1) values can vary, except the last in order to get the sum of values. |
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How does t distribution approach the normal distribution? |
As n →∞, the t distribution approaches the Z distribution. |
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Can one use the t distribution to determine the sample size? Why? |
No, because the t critical value also requires the degrees of freedom (n-1), implying that one cannot determine the required sample size mathematically. I.e. two unknowns. |
