###### Question 18 (Textile Engineering & Fibre Science)

If the length of a confidence interval on the mean of a normal distribution with known variance is to be halved, the sample size must

(A) | increase by 2 times |

(B) | decrease by 2 times |

(C) | increase by 4 times |

(D) | decrease by 4 times |

**[Show Answer]**

Confidence interval(C.I.) is directly proportional to standard error.

and

Standard error(S.E.)=

Where, n is sample size

Given,

n2=4 x n1

###### Frequently Asked Questions | FAQs

### What is the mean of normal distribution?

The mean of a normal distribution is a measure of central tendency and represents the center of the distribution. In a normal distribution, the mean is also the peak of the distribution and is often denoted by the Greek letter μ (mu).

For example, if we have a normal distribution with a mean of 50, it means that the data is centered around 50, and the highest point of the bell-shaped curve is at 50. The mean of a normal distribution is also the expected value or the average value of the random variable that follows this distribution.

In addition, the normal distribution is a symmetric distribution, so the mean is also the median and the mode of the distribution. This means that 50% of the data falls below the mean, and 50% of the data falls above the mean.

The mean of a normal distribution can be calculated using the formula:

μ = (Σx) / n

where μ is the mean, Σx is the sum of all the values in the distribution, and n is the number of values in the distribution. However, in practice, we often use statistical software or calculators to calculate the mean of a normal distribution.