Aneas arnold sells lighting supplies. she travels all over new england. her total monthly expenses for august, september, and october were $2,700, $1,100 and $2,200. what was her average monthly expenditure?

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.