Date | None Specimen | Marks available | 5 | Reference code | SPNone.3sp.hl.TZ0.1 |
Level | HL only | Paper | Paper 3 Statistics and probability | Time zone | TZ0 |
Command term | Calculate and State | Question number | 1 | Adapted from | N/A |
Question
A shopper buys 12 apples from a market stall and weighs them with the following results (in grams).
117, 124, 129, 118, 124, 116, 121, 126, 118, 121, 122, 129
You may assume that this is a random sample from a normal distribution with mean μ and variance σ2.
Determine unbiased estimates of μ and σ2.
Determine a 99 % confidence interval for μ .
The stallholder claims that the mean weight of apples is 125 grams but the shopper claims that the mean is less than this.
(i) State suitable hypotheses for testing these claims.
(ii) Calculate the p-value of the above sample.
(iii) Giving a reason, state which claim is supported by your p-value using a 5 % significance level.
Markscheme
unbiased estimate of μ=122 A1
unbiased estimate of σ2=4.4406…2=19.7 (M1)A1
Note: Award (M1)A0 for 4.44.
[3 marks]
the 99 % confidence interval for μ is [118, 126] A1A1
[2 marks]
(i) H0:μ=125; H1:μ<125 A1
(ii) p-value = 0.0220 A2
(iii) the shopper’s claim is supported because 0.0220<0.05 A1R1
[5 marks]