Find the value of $q$ .

Use your graphic display calculator to find
(i)     the mean number of fillings;
(ii)    the median number of fillings;
(iii)   the standard deviation of the number of fillings.

$q = 25 - (4 + 3 + 8 + 4 +1)$     (M1)

Note: Award (M1) for subtraction from $25$ of all values from the table.

$= 5$     (A1)     (C2)

[2 marks]

(i)     $2.2$     (A2)(ft)     (C2)

Note: Award (M1) for use of mean formula with correct substitution. Follow through from part (a), irrespective of whether working is shown.

(ii)    $2$     (A1)     (C1)

(iii)   $1.39$     (A1)(ft)     (C1)

Note: Follow through from part (a), irrespective of whether working is shown. Award (A1) for $1.38$.

[4 marks]

Part b was not well answered by the majority of candidates, indicating that the use of the GDC is not a natural tool for answering this type of question. Many students ignored the frequencies when finding the mean, median, and standard deviation.

Part b was not well answered by the majority of candidates, indicating that the use of the GDC is not a natural tool for answering this type of question. Many students ignored the frequencies when finding the mean, median, and standard deviation.