OCR MEI D1 2007 June — Question 6

Exam BoardOCR MEI
ModuleD1 (Decision Mathematics 1)
Year2007
SessionJune
TopicModelling and Hypothesis Testing
TypeMarkov chain transition simulation

6 In winter in Metland the weather each day can be classified as dry, wet or snowy. The table shows the probabilities for the next day's weather given the current day's weather.
\cline { 3 - 5 } \multicolumn{2}{c|}{}next day's weather
\cline { 3 - 5 } \multicolumn{2}{c|}{}drywetsnowy
\multirow{3}{*}{
current
day's
weather
}
dry\(\frac { 4 } { 10 }\)\(\frac { 3 } { 10 }\)\(\frac { 3 } { 10 }\)
\cline { 2 - 5 }wet\(\frac { 2 } { 10 }\)\(\frac { 5 } { 10 }\)\(\frac { 3 } { 10 }\)
\cline { 2 - 5 }snowy\(\frac { 2 } { 7 }\)\(\frac { 2 } { 7 }\)\(\frac { 3 } { 7 }\)
You are to use two-digit random numbers to simulate the winter weather in Metland.
  1. Give an efficient rule for using two-digit random numbers to simulate tomorrow's weather if today is
    (A) dry,
    (B) wet,
    (C) snowy.
  2. Today is a dry winter's day in Metland. Use the following two-digit random numbers to simulate the next 7 days' weather in Metland. $$\begin{array} { l l l l l l l l l l } 23 & 85 & 98 & 99 & 56 & 47 & 82 & 14 & 03 & 12 \end{array}$$
  3. Use your simulation from part (ii) to estimate the proportion of dry days in a Metland winter.
  4. Explain how you could use simulation to produce an improved estimate of the proportion of dry days in a Metland winter.
  5. Give two criticisms of this model of weather.