Many adults complain they do not get enough sleep at night.

what happens when these adults have children?

independent random samples of 150 adults who do not have children in the house and 130 adults who do have children in the house are selected.
the average amount of sleep the adults without children had was 7.1 hours with a standard deviation of 0.7 hours.
the average amount of sleep the adults with children had was 6.5 hours with a standard deviation of 0.8 hours.
what is the estimate for the standard deviation of the sampling distribution of the difference in sample means?