Two sets each of $20$ observations , have the same standard deviation $5$. The first set has a mean $17$ and the second a mean $22$. Determine the standard deviation of the set obtained by combining the given two sets. - Clay6.com, a Free resource for your JEE, AIPMT and Board Exam preparation

Two sets each of $20$ observations , have the same standard deviation $5$. The first set has a mean $17$ and the second a mean $22$. Determine the standard deviation of the set obtained by combining the given two sets.