SPS SPS SM Statistics (SPS SM Statistics) 2022 January

Question 1
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  1. Each day Anna drives to work.
  • R is the event that it is raining.
  • \(L\) is the event that Anna arrives at work late.
You are given that \(\mathrm { P } ( R ) = 0.36 , \mathrm { P } ( L ) = 0.25\) and \(\mathrm { P } ( R \cup L ) = 0.41\).
i. Draw a Venn diagram showing the events \(R\) and \(L\). Fill in the probability corresponding to each of the four regions of your diagram.
ii. Determine whether the events \(R\) and \(L\) are independent.
iii. Find \(\mathrm { P } ( L \mid R )\)
Question 2
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2. The temperature of a supermarket fridge is regularly checked to ensure that it is working correctly. Over a period of three months the temperature (measured in degrees Celsius) is checked 600 times. These temperatures are displayed in the cumulative frequency diagram below.
\includegraphics[max width=\textwidth, alt={}, center]{252d5094-6cdd-4379-bcd5-ca6a5cc48c7a-3_956_1497_1361_269}
i. Use the diagram to estimate the median and interquartile range of the data.
ii. Use your answers to part (i) to show that there are very few, if any, outliers in the sample. Below is the frequency table for these data:
Temperature
\(( t\) degrees Celsius \()\)
\(3.0 \leq t \leq 3.4\)\(3.4 < t \leq 3.8\)\(3.8 < t \leq 4.2\)\(4.2 < t \leq 4.6\)\(4.6 < t \leq 5.0\)
Frequency2512524315750
iii. Use the table to calculate estimates for the mean and standard deviation.
iv. The temperatures are converted from degrees Celsius to degrees Fahrenheit using the formula \(F = 1.8 C + 32\). Hence estimate the mean and standard deviation of the temperatures in degrees Fahrenheit.
Question 3
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3. The weights of Braeburn apples on display in a supermarket, measured in grams, are Normally distributed with mean 210.5 and standard deviation 15.2.
i. Find the probability that a randomly selected apple weighs at least 220 grams.
ii. 80 apples are selected at random.
a) Find the probability that more than 18 of these apples weigh at least 220 grams.
b) Find the expectation and standard deviation for the number of apples that weigh at least 220 grams.
c) State a suitable approximating distribution, including any parameters, for the number of apples that weigh at least 220 grams.
d) Explain why this approximating distribution is suitable. The supermarket also sells Cox's Orange Pippin apples. The weights of these apples, measured in grams, are Normally distributed with mean 185 and standard deviation \(\sigma\).
iii. Given that \(10 \%\) of randomly selected Cox's Orange Pippin apples weigh less than 170 grams, calculate the value of \(\sigma\).