Construct a 90% confidence interval estimate of the difference between the mean IQ score for those with a low lead level and the mean IQ score for those with a high lead level. (5 marks)
Low Lead Level: n=78, x ̅=92.88462, s=15.34451
High Lead Level: n=21, x ̅=86.90476, s=8.988352

Question

Construct a 90% confidence interval estimate of the difference between the mean IQ score for those with a low lead level and the mean IQ score for those with a high lead level. (5 marks)
Low Lead Level: 	n=78,   x ̅=92.88462,   s=15.34451
High Lead Level: 	n=21,   x ̅=86.90476,   s=8.988352

anonymous · Answer

Just do a standard distribution:
$$
IC^\pm=\bar{x}\pm \Phi^{-1}(z)\frac{s}{\sqrt n}
$$