AQA S1 (Statistics 1) 2014 June

Question 1 2 marks
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1 Henrietta lives on a small farm where she keeps some hens.
For a period of 35 weeks during the hens' first laying season, she records, each week, the total number of eggs laid by the hens. Her records are shown in the table.
Total number of eggs laid in a week ( \(\boldsymbol { x }\) )Number of weeks ( f)
661
672
683
695
707
718
724
732
742
751
Total35
  1. For these data:
    1. state values for the mode and the range;
    2. find values for the median and the interquartile range;
    3. calculate values for the mean and the standard deviation.
  2. Each week, for the 35 weeks, Henrietta sells 60 eggs to a local shop, keeping the remainder for her own use. State values for the mean and the standard deviation of the number of eggs that she keeps.
    [0pt] [2 marks]
Question 2 3 marks
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2 A garden centre sells bamboo canes of nominal length 1.8 metres. The length, \(X\) metres, of the canes can be modelled by a normal distribution with mean 1.86 and standard deviation \(\sigma\).
  1. Assuming that \(\sigma = 0.04\), determine:
    1. \(\mathrm { P } ( X < 1.90 )\);
    2. \(\mathrm { P } ( X > 1.80 )\);
    3. \(\mathrm { P } ( 1.80 < X < 1.90 )\);
    4. \(\mathrm { P } ( X \neq 1.86 )\).
  2. It is subsequently found that \(\mathrm { P } ( X > 1.80 ) = 0.98\). Determine the value of \(\sigma\).
    [0pt] [3 marks]
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Question 3 4 marks
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3 The table shows the colour of hair and the colour of eyes of a sample of 750 people from a particular population.
Question 4
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4 Every year, usually during early June, the Isle of Man hosts motorbike races. Each race consists of three consecutive laps of the island's course. To compete in a race, a rider must first complete at least one qualifying lap. The data refer to the lightweight motorbike class in 2012 and show, for each of a random sample of 10 riders, values of $$u = x - 100 \quad \text { and } \quad v = y - 100$$ where
\(x\) denotes the average speed, in mph, for the rider's fastest qualifying lap and
\(y\) denotes the average speed, in mph, for the rider's three laps of the race.
\cline { 2 - 11 } \multicolumn{1}{c|}{}Rider
\cline { 2 - 11 } \multicolumn{1}{c|}{}\(\mathbf { A }\)\(\mathbf { B }\)\(\mathbf { C }\)\(\mathbf { D }\)\(\mathbf { E }\)\(\mathbf { F }\)\(\mathbf { G }\)\(\mathbf { H }\)\(\mathbf { I }\)\(\mathbf { J }\)
\(\boldsymbol { u }\)7.8813.024.292.886.267.033.6011.7813.1511.69
\(\boldsymbol { v }\)6.6310.163.630.475.708.013.307.3113.0811.82
    1. Calculate the value of \(r _ { u v }\), the product moment correlation coefficient between \(u\) and \(v\).
    2. Hence state the value of \(r _ { x y }\), giving a reason for your answer.
  1. Interpret your value of \(r _ { x y }\) in the context of this question.
Question 5 2 marks
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5 An analysis of the number of vehicles registered by each household within a city resulted in the following information.
Number of vehicles registered012\(\geqslant 3\)
Percentage of households18472510
  1. A random sample of 30 households within the city is selected. Use a binomial distribution with \(n = 30\), together with relevant information from the table in each case, to find the probability that the sample contains:
    1. exactly 3 households with no registered vehicles;
    2. at most 5 households with three or more registered vehicles;
    3. more than 10 households with at least two registered vehicles;
    4. more than 5 households but fewer than 10 households with exactly two registered vehicles.
  2. If a random sample of \(\mathbf { 1 5 0 }\) households within the city were to be selected, estimate the mean and the variance for the number of households in the sample that would have either one or two registered vehicles.
    [0pt] [2 marks]
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Question 6 3 marks
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6 A rubber seal is fitted to the bottom of a flood barrier. When no pressure is applied, the depth of the seal is 15 cm . When pressure is applied, a watertight seal is created between the flood barrier and the ground. The table shows the pressure, \(x\) kilopascals ( kPa ), applied to the seal and the resultant depth, \(y\) centimetres, of the seal.
\(\boldsymbol { x }\)255075100125150175200250300
\(\boldsymbol { y }\)14.713.412.811.911.010.39.79.07.56.7
    1. State the value that you would expect for \(a\) in the equation of the least squares regression line, \(y = a + b x\).
    2. Calculate the equation of the least squares regression line, \(y = a + b x\).
    3. Interpret, in context, your value for \(b\).
  1. Calculate an estimate of the depth of the seal when it is subjected to a pressure of 225 kPa .
    1. Give a statistical reason as to why your equation is unlikely to give a realistic estimate of the depth of the seal if it were to be subjected to a pressure of 400 kPa .
    2. Give a reason based on the context of this question as to why your equation will not give a realistic estimate of the depth of the seal if it were to be subjected to a pressure of 525 kPa .
      [0pt] [3 marks]
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Question 7
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7 The volume of water, \(V\), used by a guest in an en suite shower room at a small guest house may be modelled by a random variable with mean \(\mu\) litres and standard deviation 65 litres. A random sample of 80 guests using this shower room showed a mean usage of 118 litres of water.
    1. Give a numerical justification as to why \(V\) is unlikely to be normally distributed.
    2. Explain why \(\bar { V }\), the mean of a random sample of 80 observations of \(V\), may be assumed to be approximately normally distributed.
    1. Construct a \(98 \%\) confidence interval for \(\mu\).
    2. Hence comment on a claim that \(\mu\) is 140 .
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