Date | May 2014 | Marks available | 2 | Reference code | 14M.1.sl.TZ2.12 |
Level | SL only | Paper | 1 | Time zone | TZ2 |
Command term | Find | Question number | 12 | Adapted from | N/A |
Question
A survey investigated the relationship between the number of cleaners, n, and the amount of time, t, it takes them to clean a school.

Use your graphic display calculator to write down the equation of the regression line t on n.
Write down the value of the Pearson’s product–moment correlation coefficient, r.
Use your regression equation to find the amount of time 4 cleaners take to clean the school.
Markscheme
t=−20.1n+205
t=(−20.1046…)n+(204.755…) (A1)(A1) (C2)
Notes: Award (A1) for −20.1 and 205 seen,
(A1) for an equation involving t and n.
[2 marks]
−0.941(−0.941366…) (A2) (C2)
Notes: Award (A0)(A1) for +0.941.
[2 marks]
−20.1046…×4+204.755… (M1)
Note: Award (M1) for substitution into their regression equation.
124 (minutes) (124.337…) (A1)(ft) (C2)
Notes: Follow through from their regression equation found in part (a). Accept 125 (minutes) (124.6).
[2 marks]