I need detailed explanation on how to solve this problem and

I need detailed explanation on how to solve this problem and what type to hypothesis testing to use:

All pacemakers generate a pulse of current to depolarize a bit of the heart, the wave then spontaneously spreads to the rest of that part of the heart. Pulse duration is programmable in all currently manufactured permanent pacemakers. The shorter the pulse, the greater the necessary current. The length of the pulse for a particular setting will vary due to random fluctuations such that the actual pulse length is normally distributed with a mean equal to the setting and with an unknown variance sigma^2. A type of pacemaker is claimed to be reliable since its standard deviation a is less than 0.10. If a random sample of 20 pacemakers of that type resulted in a sample standard deviation of 0.08, should this claim be accepted? Suppose the level of significance is alpha = 0.05.

Solution

Sample standard deviation = sigma / sqrt(n)

0.08= x /sqrt(20)

=>x=0.357

This claim cannot be excepted .

Null Hyputhesis .