Sample Statistics Questions
Q1: A dataset has values: 2, 4, 4, 6, 8. What is the median?
Q2: Which of the following correctly describes a Type I error?
A. Failing to reject a false null hypothesis
B. Rejecting a true null hypothesis ✓
C. Accepting a false alternative hypothesis
D. Failing to reject a true null hypothesis
Q3: A normal distribution is described as:
A. Right-skewed with a long tail
B. Symmetric and bell-shaped ✓
C. Uniform across all values
D. Bimodal with two peaks
📖 Study Tips for Statistics
1
Always distinguish between a population parameter (fixed, often unknown) and a sample statistic (calculated from data, used to estimate the parameter).
2
Visualize data distributions before calculating — a histogram or boxplot reveals skew, outliers, and spread that summary statistics can hide.
3
For hypothesis testing, identify H₀ and H₁ first, then choose the correct test (z-test, t-test, chi-square) based on the data type and sample size.
4
Understand what a p-value actually means: the probability of observing data at least as extreme as yours, assuming H₀ is true — not the probability H₀ is true.
❓ Statistics FAQ
What is the difference between the mean, median, and mode?
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The mean is the arithmetic average. The median is the middle value when data is ordered. The mode is the most frequent value. The median is preferred for skewed data because it is not influenced by extreme outliers the way the mean is.
What does a 95% confidence interval mean?
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A 95% confidence interval means that if we repeated the sampling procedure many times, 95% of the resulting intervals would contain the true population parameter. It does NOT mean there is a 95% chance the parameter is in this specific interval.
What is the difference between correlation and causation?
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Correlation measures the strength and direction of a linear relationship between two variables. Causation means one variable directly causes changes in another. A correlation does not imply causation — both variables might be caused by a third (confounding) variable.
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