Statistics: Mean, Median, Variance, and p-values
Intro stats exam cards — central tendency, spread, sampling basics, and interpreting p-values carefully.
12 cards· by GuruOwl
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Try it- 01What is the mean?The arithmetic average: sum of values divided by the number of values.center
- 02What is the median?The middle value when data are ordered (average of two middle values if even n). Robust to outliers.center
- 03When is the median preferred over the mean?When the distribution is skewed or has extreme outliers.center
- 04What is variance?Average squared deviation from the mean — measures spread. Population σ² vs sample s² (n−1).spread
- 05What is standard deviation?Square root of variance — spread in original units.spread
- 06What is a sampling distribution?The distribution of a statistic (e.g., sample mean) across repeated samples from the same population.inference
- 07What does the Central Limit Theorem say (informal)?For large enough n, the sampling distribution of the mean is approximately normal even if the population is not (finite variance).inference
- 08What is a p-value?The probability, under the null hypothesis, of seeing data as extreme as (or more extreme than) observed.pvalue
- 09Does p < 0.05 prove the alternative hypothesis is true?No — it indicates data are unlikely under the null (given assumptions); it is not the probability the null is true.pvalue
- 10What is a Type I error?Rejecting a true null hypothesis (false positive). Rate controlled by α.errors
- 11What is a Type II error?Failing to reject a false null hypothesis (false negative). Related to power (1 − β).errors
- 12What is a confidence interval (interpret carefully)?A range computed so that, in repeated sampling, a stated percentage (e.g., 95%) of such intervals would contain the true parameter — not “95% probability this interval contains it” in the frequentist sense after seeing the data.ci