Statistics practice problems with worked answers
You do the maths: mean, standard deviation, probabilities and distributions. Five problems, new every day, with worked solutions and the typical mistake. Free and without an account.
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Task
The random variable X has this distribution. Work out the expected value and the variance.
| x | P(X = x) |
|---|---|
| 0 | 0.40 |
| 1 | 0.20 |
| 2 | 0.20 |
| 5 | 0.20 |
E(X) (2 decimal places)
Var(X) (2 decimal places)
Comma or point; fractions like 1/6 work too.
Topics with formulas and practiceMean, median and mode · Variance and standard deviation · Combinatorics and probability · Expected value and variance …
How the trainer works
Do the maths yourself
Type the result with a comma or point, fractions like 1/6 work too. Small rounding differences are accepted.
Step-by-step working
After checking you see the formula, the steps and the typical mistake for this problem.
Like in the exam
Critical values and quantiles are given in the problem, just like with the table in the exam.