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Statistical distributions

3 dot points across 3 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

When does the binomial distribution apply, and how do you use it?

Characteristics of a binomial distribution; the notation B(n, p); the conditions for a binomial model; the mean np; calculating binomial probabilities for n up to 10.
A focused answer to Edexcel GCSE Statistics (Higher tier) on the binomial distribution, covering its characteristics, the notation B(n, p), the conditions that make a binomial model suitable, the mean np, and calculating binomial probabilities for n up to 10.
9 min answer →

How do control charts with warning and action lines monitor a process?

Sample means are less spread than individual values; control charts for sample mean, median or range; warning lines at two standard deviations and action lines at three; the action to take when a value falls outside a limit.
A focused answer to Edexcel GCSE Statistics (Higher tier) on quality assurance, covering why sample means are less spread than individual values, control charts for the sample mean, median or range, warning lines at two standard deviations and action lines at three, and the action to take when a value falls outside a limit.
9 min answer →

What are the features of a Normal distribution, and what proportions lie within one, two and three standard deviations?

Characteristics of a Normal distribution; the notation N(mu, sigma squared); the symmetrical bell shape with equal mean, median and mode; the 68, 95 and 99.7 per cent proportions; conditions for a Normal model.
A focused answer to Edexcel GCSE Statistics (Higher tier) on the Normal distribution, covering its symmetrical bell shape, the notation N(mu, sigma squared), equal mean, median and mode, the proportions within one, two and three standard deviations, and the conditions that make a Normal model suitable.
9 min answer →