Question

The average age of a breed of dog is 19.5 years. if the distribution of their ages is normal and 20% of dogs are older than 22.6 years, find the standard deviation.

Answer 1

The  standard deviation of the average age of a breed of dog  is said to be 3.69.

What is the standard deviation about?

Note that we take:

• x = dog age has mean 19.5
• Unknown standard deviation.

Hence:

z = (x - mean) /SD is distributed N (0,1) - mean o standard deviation 1 (standard normal)

Since 20% of dogs are known to be older than 22.6 years:

So 22.6 years is said to be 80th percentile,

Since z matching to 80th percentile (using the standard normal table) s is 0.84.

Then one need to plug z, x which is  = 22.6

mean = 19.5 into the stated z equation:

Hence,

0.84 = (22.6 - 19.5)/SD

SD = (22.6 - 19.5)/0.84

= 3.69

Learn more about standard deviation from

brainly.com/question/475676

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