A company makes 140 bags. 30 of the bags have buttons but no zips.
27 of the bags have zips but no buttons.
20 of the bags have neither zips nor buttons.
A bag is selected at random.
What is the probability that the bag has buttons?

Scores on the cognitive scale of the bayley-scales of infant and toddler development range from 1 to 19, with a standard deviation of 3. calculate the margin of error in estimating the true mean cognitive scale score, with 99% confidence, if there are 12 infants and toddlers in a sample.