Easy -1.2 This is a straightforward application of the coded data formulas for mean and standard deviation. Students need to recall that mean = 35 + (-15)/12 and use the variance formula with coded sums, requiring only direct substitution into standard formulas with no problem-solving or conceptual insight.
1 The length of time, \(t\) minutes, taken to do the crossword in a certain newspaper was observed on 12 occasions. The results are summarised below.
$$\Sigma ( t - 35 ) = - 15 \quad \Sigma ( t - 35 ) ^ { 2 } = 82.23$$
Calculate the mean and standard deviation of these times taken to do the crossword.
1 The length of time, $t$ minutes, taken to do the crossword in a certain newspaper was observed on 12 occasions. The results are summarised below.
$$\Sigma ( t - 35 ) = - 15 \quad \Sigma ( t - 35 ) ^ { 2 } = 82.23$$
Calculate the mean and standard deviation of these times taken to do the crossword.
\hfill \mbox{\textit{CAIE S1 2007 Q1 [4]}}