Edexcel S2 2019 January — Question 3

Exam BoardEdexcel
ModuleS2 (Statistics 2)
Year2019
SessionJanuary
TopicCumulative distribution functions
TypeCalculate probabilities from CDF

3. Figure 1 shows an accurate graph of the cumulative distribution function, \(\mathrm { F } ( x )\), for the continuous random variable \(X\) \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{17296edc-9ab4-4f81-ae68-c76190986fd1-08_535_1152_354_342} \captionsetup{labelformat=empty} \caption{Figure 1}
\end{figure}
  1. Find \(\mathrm { P } ( 3 < X < 7 )\) The probability density function of \(X\) is given by $$\mathrm { f } ( x ) = \begin{cases} a & 2 \leqslant x < 4
    b & 4 \leqslant x < 6
    c & 6 \leqslant x \leqslant 8
    0 & \text { otherwise } \end{cases}$$ where \(a\), \(b\) and \(c\) are constants.
  2. Find the value of \(a\), the value of \(b\) and the value of \(c\)
  3. Find \(\mathrm { E } ( X )\)