I- Using step-deviation method- calculate the mean marks of the following distribution- ii- State the modal class- - Class-interval amp- Frequency- 50-55 amp- 5- 55-60 amp- 20- 60-65 amp- 10- 65-70 amp- 10- 70-75 amp- 9- 75-80 amp- 6- 80-85 amp- 12- 85-90 amp- 8- -4 MARKS-

Step deviation method: 3 Marks Modal Class: 1 Mark [ Class amp; Frequency amp; x amp; u =x A/h amp; fu; interval amp; (f) ...

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Standard X

Mathematics

Class Interval

i) Using step...

Question

i) Using step-deviation method, calculate the mean marks of the following distribution.
ii) State the modal class.
$\begin{matrix} C l a s s i n t e r v a l & F r e q u e n c y 50 - 55 & 5 55 - 60 & 20 60 - 65 & 10 65 - 70 & 10 70 - 75 & 9 75 - 80 & 6 80 - 85 & 12 85 - 90 & 8 \end{matrix}$ [4 MARKS]

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Solution

Step deviation method: 3 Marks
Modal Class: 1 Mark

$\begin{matrix} C l a s s & F r e q u e n c y & x & u = \frac{x - A}{h} & f u i n t e r v a l & (f) 50 - 55 & 5 & 52.5 & - 3 & - 15 55 - 60 & 20 & 57.5 & - 2 & - 40 60 - 65 & 10 & 62.5 & - 1 & - 10 65 - 70 & 10 & 67.5 = A & 0 & 0 70 - 75 & 9 & 72.5 & 1 & 9 75 - 80 & 6 & 77.5 & 2 & 12 80 - 85 & 12 & 82.5 & 3 & 36 85 - 90 & 8 & 87.5 & 4 & 32 \sum f = 80 & \sum f u = 24 \end{matrix}$
$∴$ Mean $= A + h \frac{\sum f u}{\sum f} = 67.5 + 5 \times \frac{24}{80}$
= 67.5 + 1.5 = 69

ii) Modal class is 55 - 60

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i) Using step-deviation method, calculate the mean marks of the following distribution. ii) State the modal class. Class intervalFrequency50−55555−602060−651065−701070−75975−80680−851285−908 [4 MARKS]