How to Take This Test
The 25 questions are mixed the way the statistics questions of a Tier 2 paper are: means of lists and of grouped tables, medians and modes by formula, missing values found from a given mean, median or mode, the empirical relation, and spread (standard deviation, variance, coefficient of variation). At one minute a question there is no time to copy out a whole table, so write only the column the question needs, such as the cumulative frequencies for a median or the three frequencies around the modal class for a mode, and use the rules for adding to or multiplying every value instead of working the data out again.
Work without a calculator or notes, with a 25-minute timer running. Each right answer earns 3 marks and each wrong one costs 1; a question left blank costs nothing. Before you work anything out, cross off options that cannot be right: a mean, median or mode lies between the smallest and the largest value, a median or mode found by formula lies inside its class, and a standard deviation is never negative. Read the explanations once the 25 minutes are over.
Working out your score. The maximum is 75. With 21 right, 2 wrong and 2 left blank you score .
| Score (out of 75) | What to do next |
|---|---|
| 60 or more | You can handle this chapter at exam speed. Redo one PYQ Practice Set every week or two so the formulas stay fresh. |
| 45 to 59 | Most methods are in place, but one or two kinds of question are costing marks. Group your wrong answers by their tag and redo the quiz of the section they point to: Mean, Median, Mode and the Empirical Formula, or Range, Variance and Standard Deviation. |
| 30 to 44 | The formulas are known, but grouped tables are going wrong or taking too long. Practise the four-line median and the lean check for the mode in Shortcuts & Speed Methods, time yourself on Practice Sets 2 and 3, and come back to this test after a few days. |
| Below 30 | Go back to Mean and Median with their quizzes, then Mode and the Empirical Formula, and read the worked questions in Solved Questions before any more timed work. |
On guessing: with +3 and , a blind guess is worth nothing on average, since . Once one option has been struck out, a guess is worth a third of a mark on average, and with two struck out it is worth a full mark, so guess only after ruling out at least one option.