19N.2.SL.TZ0.S_1

pestleMathematicsAASLPaper 219N· sl-4-4-pearsons-scatter-diagrams-eqn-of-y-on-xsource ↗

The number of messages, $M$ , that six randomly selected teenagers sent during the month of October is shown in the following table. The table also shows the time, $T$ , that they spent talking on their phone during the same month.

The relationship between the variables can be modelled by the regression equation $M = aT + b$ .

Write down the value of $a$ and of $b$ .

[3]

Use your regression equation to predict the number of messages sent by a teenager that spent $154$ minutes talking on their phone in October.

[3]

Markscheme / solution

evidence of set up (M1)

eg correct value for $a$ or $b$ (accept $r = 0.966856$ )

$4.30161$ , $163.330$

$a = 4.30$ , $b = 163$ (accept $y = 4.30x + 163$ ) A1A1 N3

[3 marks]

valid approach (M1)

eg $4.30\left( {154} \right) + 163$

eg $825.778$ ( $825.2$ from 3 sf values) (A1)

number of messages $= 826$ (must be an integer) A1 N3

[3 marks]

Examiners’ report

[N/A]