Calculating expected frequency

Sample Calculating expected frequency questions

A few of the 34 questions, from easier to harder. Choose your exam board and tier to practise them, with every answer marked.

1. Question 11 markGrade 2
   The probability of Heads when a biased coin is thrown is 0.6. The coin is thrown 500 times. Which is the expected number of Tails? 20, 200, 250, 300
   Show the worked solution

   P(Tails) = 1 - 0.6 = 0.4.

   Expected Tails = 500 × 0.4 = 200.
2. Question 23 marksGrade 3-4
   A fair 4-sided spinner is rolled 16 times. (a) If the spinner is fair, work out the expected number of times the number 4 should occur. (b) In the experiment, the number 4 occurred 9 times. By how many more or fewer than expected did this outcome occur?
   Show the worked solution

   (a) Probability of the outcome = $\frac{1}{4}$

What are the common mistakes in Calculating expected frequency?

When a pupil makes one of these on Revision Workshop, the marking engine names the mistake and explains it, instead of just marking the answer wrong.

• Gives the probability as the final answer where the expected frequency (count) was asked for, or vice versa

  Compared the actual frequency to the probability $\frac{1}{4}$ instead of to the expected frequency (4), which requires multiplying by the number of trials first

• Picks the smaller of two possible gaps/differences instead of the larger one asked for

  Gave the smaller of the two differences (1) instead of identifying the larger gap, which shows the outcome further from what's expected

• Compares raw frequency values rather than the differences (gaps) between them

  Compared the actual frequencies (13 and 14) directly instead of comparing how far each is from the expected frequency (6)

Quick answers about Calculating expected frequency

How many Calculating expected frequency practice questions are there?

There are 34 self-marking GCSE and IGCSE Maths questions on Calculating expected frequency, written for AQA, Pearson, OCR, Pearson International GCSE Maths A (4MA1), Cambridge IGCSE Mathematics (0580), Cambridge IGCSE (9-1) Mathematics (0980) across Foundation and Higher and Core and Extended tier. Each one is marked instantly and has a full worked solution.

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