Question

If the mean of the following data is 17 then the value of p is

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$$\begin{array}{cccccc}X& \text{10}& \text{p}& \text{18}& \text{21}& \text{25}\\ F& \text{10}& \text{15}& \text{7}& \text{9}& \text{9}\end{array}$$

Answer 1

$$\begin{array}{ccc}X& F& FX\\ \text{10}& \text{10}& \text{100}\\ \text{p}& \text{15}& \text{15p}\\ \text{18}& \text{7}& \text{126}\\ \text{21}& \text{9}& \text{189}\\ \text{25}& \text{9}& \text{225}\end{array}$$

$\sum F=50$
$\sum FX=640+15p$
Given mean=17
$17=\frac{640+15p}{50}\Rightarrow 15p=50\times 17-640=210\Rightarrow p=\frac{210}{15}=14$