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The mean of 15 observations is 40. It was detected that one observation 47 was misread as 77. Find the correct mean. - Mathematics

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Question

The mean of 15 observations is 40. It was detected that one observation 47 was misread as 77. Find the correct mean.

Sum
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Solution

Given: The mean of 15 observations is 40 and one observation 47 was misread as 77.

Step-wise calculation:

1. Original (erroneous) total

= 15 × 40

= 600

2. The recorded data includes 77 instead of the true 47.

So, correct total

= 600 – 77 + 47

= 600 – 30

= 570

3. Correct mean

= 570 ÷ 15

= 38

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Chapter 15: Statistics - Exercise 15C [Page 303]

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Nootan Mathematics [English] Class 9 ICSE
Chapter 15 Statistics
Exercise 15C | Q 8. | Page 303
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