Sketch or interpret PDF graph

A question is this type if and only if it asks to sketch the probability density function or interpret features from a given graph of the PDF.

7 questions · Moderate -0.2

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CAIE S2 2007 June Q7
11 marks Moderate -0.3
7 The continuous random variable \(X\) has probability density function given by $$f ( x ) = \begin{cases} \frac { 3 } { 4 } \left( x ^ { 2 } - 1 \right) & 1 \leqslant x \leqslant 2 \\ 0 & \text { otherwise } \end{cases}$$
  1. Sketch the probability density function of \(X\).
  2. Show that the mean, \(\mu\), of \(X\) is 1.6875 .
  3. Show that the standard deviation, \(\sigma\), of \(X\) is 0.2288 , correct to 4 decimal places.
  4. Find \(\mathrm { P } ( 1 \leqslant X \leqslant \mu + \sigma )\).
CAIE S2 2011 November Q7
12 marks Moderate -0.3
7 \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{3629cb5c-fb4c-43b1-b43f-ce321411b814-3_385_385_982_246} \captionsetup{labelformat=empty} \caption{Fig. 1}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{3629cb5c-fb4c-43b1-b43f-ce321411b814-3_385_380_982_669} \captionsetup{labelformat=empty} \caption{Fig. 2}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{3629cb5c-fb4c-43b1-b43f-ce321411b814-3_390_378_977_1087} \captionsetup{labelformat=empty} \caption{Fig. 3}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{3629cb5c-fb4c-43b1-b43f-ce321411b814-3_390_391_977_1503} \captionsetup{labelformat=empty} \caption{Fig. 4}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{3629cb5c-fb4c-43b1-b43f-ce321411b814-3_392_391_1475_370} \captionsetup{labelformat=empty} \caption{Fig. 5}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{3629cb5c-fb4c-43b1-b43f-ce321411b814-3_392_387_1475_872} \captionsetup{labelformat=empty} \caption{Fig. 6}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{3629cb5c-fb4c-43b1-b43f-ce321411b814-3_392_389_1475_1375} \captionsetup{labelformat=empty} \caption{Fig. 7}
\end{figure} Each of the random variables \(T , U , V , W , X , Y\) and \(Z\) takes values between 0 and 1 only. Their probability density functions are shown in Figs 1 to 7 respectively.
  1. (a) Which of these variables has the largest median?
    (b) Which of these variables has the largest standard deviation? Explain your answer.
  2. Use Fig. 2 to find \(\mathrm { P } ( U < 0.5 )\).
  3. The probability density function of \(X\) is given by $$f ( x ) = \begin{cases} a x ^ { n } & 0 \leqslant x \leqslant 1 \\ 0 & \text { otherwise } \end{cases}$$ where \(a\) and \(n\) are positive constants.
    (a) Show that \(a = n + 1\).
    (b) Given that \(\mathrm { E } ( X ) = \frac { 5 } { 6 }\), find \(a\) and \(n\).
CAIE S2 2011 November Q7
12 marks Moderate -0.3
7 \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{6e90d172-0292-4bb6-9d4a-506669076d4e-3_385_385_982_246} \captionsetup{labelformat=empty} \caption{Fig. 1}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{6e90d172-0292-4bb6-9d4a-506669076d4e-3_385_380_982_669} \captionsetup{labelformat=empty} \caption{Fig. 2}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{6e90d172-0292-4bb6-9d4a-506669076d4e-3_390_378_977_1087} \captionsetup{labelformat=empty} \caption{Fig. 3}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{6e90d172-0292-4bb6-9d4a-506669076d4e-3_390_391_977_1503} \captionsetup{labelformat=empty} \caption{Fig. 4}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{6e90d172-0292-4bb6-9d4a-506669076d4e-3_392_391_1475_370} \captionsetup{labelformat=empty} \caption{Fig. 5}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{6e90d172-0292-4bb6-9d4a-506669076d4e-3_392_387_1475_872} \captionsetup{labelformat=empty} \caption{Fig. 6}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{6e90d172-0292-4bb6-9d4a-506669076d4e-3_392_389_1475_1375} \captionsetup{labelformat=empty} \caption{Fig. 7}
\end{figure} Each of the random variables \(T , U , V , W , X , Y\) and \(Z\) takes values between 0 and 1 only. Their probability density functions are shown in Figs 1 to 7 respectively.
  1. (a) Which of these variables has the largest median?
    (b) Which of these variables has the largest standard deviation? Explain your answer.
  2. Use Fig. 2 to find \(\mathrm { P } ( U < 0.5 )\).
  3. The probability density function of \(X\) is given by $$f ( x ) = \begin{cases} a x ^ { n } & 0 \leqslant x \leqslant 1 \\ 0 & \text { otherwise } \end{cases}$$ where \(a\) and \(n\) are positive constants.
    (a) Show that \(a = n + 1\).
    (b) Given that \(\mathrm { E } ( X ) = \frac { 5 } { 6 }\), find \(a\) and \(n\).
AQA Further AS Paper 2 Statistics Specimen Q6
8 marks Moderate -0.3
6 The continuous random variable \(T\) has probability density function defined by $$\mathrm { f } ( t ) = \left\{ \begin{array} { c c } \frac { 1 } { 3 } & 0 \leq t \leq \frac { 3 } { 2 } \\ \frac { 9 - 2 t } { 18 } & \frac { 3 } { 2 } \leq t \leq \frac { 9 } { 2 } \\ 0 & \text { otherwise } \end{array} \right.$$ 6
    1. Sketch this probability density function below. \includegraphics[max width=\textwidth, alt={}, center]{6ccf7d1d-5a7b-47d1-b38e-c7e762204746-07_1009_1041_1073_520} 6
      1. (ii) State the median of \(T\). 6
      1. Find \(\mathrm { E } ( T )\) [0pt] [2 marks]
        6
    2. (ii) Given that \(\mathrm { E } \left( T ^ { 2 } \right) = \frac { 15 } { 4 }\), find \(\operatorname { Var } ( 4 T - 5 )\) [3 marks]
AQA Further AS Paper 2 Statistics 2018 June Q5
5 marks Moderate -0.3
5 The diagram shows a graph of the probability density function of the random variable \(X\). \includegraphics[max width=\textwidth, alt={}, center]{313cd5ce-07ff-4781-a134-565b8b221145-05_574_1086_406_479} 5
  1. State the mode of \(X\).
    5
  2. Find the probability density function of \(X\).
Edexcel S2 2002 June Q7
17 marks Moderate -0.3
The continuous random variable \(X\) has probability density function $$f(x) = \begin{cases} \frac{x}{15}, & 0 \leq x \leq 2, \\ \frac{2}{15}, & 2 < x < 7, \\ \frac{4}{9} - \frac{2x}{45}, & 7 \leq x \leq 10, \\ 0, & \text{otherwise}. \end{cases}$$
  1. Sketch \(f(x)\) for all values of \(x\). [3]
    1. Find expressions for the cumulative distribution function, \(\mathrm{F}(x)\), for \(0 \leq x \leq 2\) and for \(7 \leq x \leq 10\).
    2. Show that for \(2 < x < 7\), \(\mathrm{F}(x) = \frac{2x}{15} - \frac{2}{15}\).
    3. Specify \(\mathrm{F}(x)\) for \(x < 0\) and for \(x > 10\).
    [8]
  2. Find \(\mathrm{P}(X \leq 8.2)\). [2]
  3. Find, to 3 significant figures, \(\mathrm{E}(X)\). [4]
AQA S2 2016 June Q7
9 marks Standard +0.3
The continuous random variable \(X\) has a cumulative distribution function F(\(x\)), where $$\text{F}(x) = \begin{cases} 0 & x < 1 \\ \frac{1}{4}(x - 1) & 1 \leqslant x < 4 \\ \frac{1}{16}(12x - x^2 - 20) & 4 \leqslant x \leqslant 6 \\ 1 & x > 6 \end{cases}$$
  1. Sketch the probability density function, f(\(x\)), on the grid below. [5 marks]
  2. Find the mean value of \(X\). [4 marks]