| Date | May 2008 | Marks available | 1 | Reference code | 08M.1.sl.TZ2.5 |
| Level | SL only | Paper | 1 | Time zone | TZ2 |
| Command term | Write down | Question number | 5 | Adapted from | N/A |
Question
A survey was conducted of the number of bedrooms in \(208\) randomly chosen houses. The results are shown in the following table.
State whether the data is discrete or continuous.
Write down the mean number of bedrooms per house.
Write down the standard deviation of the number of bedrooms per house.
Find how many houses have a number of bedrooms greater than one standard deviation above the mean.
Markscheme
Discrete (A1) (C1)
[1 mark]
For attempting to find \(\sum fx/\sum f\) (M1)
\(2.73\) (A1) (C2)
Note: for (b) and (c), if both mean and standard deviation given to 2 significant figures.
Award (C1)(C0)(AP) for \(2.7\). Award (A1)(ft) for \(1.3\) ((AP) already deducted).
[2 marks]
\(1.34\) (A1) (C1)
Note: for (b) and (c), if both mean and standard deviation given to 2 significant figures.
Award (C1)(C0)(AP) for \(2.7\). Award (A1)(ft) for \(1.3\) ((AP) already deducted).
[1 mark]
Attempt to find their mean \( + \) their standard deviation (can be implied) (M1)
\(23\), (ft) their mean and standard deviation. (A1)(ft) (C2)
[2 marks]
Examiners report
Many candidates did not use the calculator correctly to find the mean and standard deviation, trying to do all the calculations by hand with a significant number not realizing it was a frequency table – this could have been the error with those using the calculator also as few received full marks on this question. When the candidate had made an error follow through marks could be awarded for the final part provided working had been shown. Most knew the data was discrete.
Many candidates did not use the calculator correctly to find the mean and standard deviation, trying to do all the calculations by hand with a significant number not realizing it was a frequency table – this could have been the error with those using the calculator also as few received full marks on this question. When the candidate had made an error follow through marks could be awarded for the final part provided working had been shown. Most knew the data was discrete.
Many candidates did not use the calculator correctly to find the mean and standard deviation, trying to do all the calculations by hand with a significant number not realizing it was a frequency table – this could have been the error with those using the calculator also as few received full marks on this question. When the candidate had made an error follow through marks could be awarded for the final part provided working had been shown. Most knew the data was discrete.
Many candidates did not use the calculator correctly to find the mean and standard deviation, trying to do all the calculations by hand with a significant number not realizing it was a frequency table – this could have been the error with those using the calculator also as few received full marks on this question. When the candidate had made an error follow through marks could be awarded for the final part provided working had been shown. Most knew the data was discrete.
