1. According to the empirical rule, if the data form a "bell-shaped" normal distribution, ________ percent of the observation will be contained within 1 (one) standard deviation around the arithmetic mean.
2. The probability that a new advertising campaign will increase sales is assessed as being 0.80. The probability that the cost of developing the new add campaign can be kept within the original budget allocation is 0.40. Assuming that the two events are independent, the probability that the cost is kept withing budget and the campaign will increase sales is:
1. +1 sigma is 34.1% and -1 sigma is also 34.1%, so the percentage ...