Two years ago “Illyria” decided to enter the chocolate market,
and it began by producing vanilla flavored chocolate called
“Vanchoc”. The company’s sales of chocolate are higher than
expected, and consumers’ ratings of the product have a mean of 75
and a standard deviation of 25 on a 100-point scale for which 100
is the most favorable score and zero is the least favorable score.
Past experience has also shown Illyria that a consumer who rates
one of its products with a score greater than 70 on this scale will
consider purchasing the product, and a score of 70 or less
indicates that the consumer will not consider purchasing the
product. Encouraged by these results, Illyria is now considering
the introduction of a second flavor, a strawberry flavored
chocolate that would be called “Strawchoc”, but managers are
concerned about whether or not Strawchoc will increase Illyrias’s
market share by appealing to potential customers who do not like
Vanchoc. That is, the goal in offering the new product is to
increase the market share rather than cannibalize existing sales of
Vanchoc. The marketing department has proposed giving tastes of
both Vanchoc and Strawchoc to a simple random sample of 50
customers and asking each of them to rate the two chocolates on the
100-point scale. If the mean score given to Vanchoc by this sample
of consumers is 70 or less, Illyria’s senior management believes
the sample can be used to assess whether Strawchoc will appeal to
potential customers who do not like Vanchoc.
1. Calculate the probability that the mean score of Vanchoc
given by the simple random sample of Illyria’s customers will be 70
or less. (10 pts)
2. If the marketing department increases the sample size to
150, what is the probability that the mean score of Vanchoc given
by the simple random sample of Illyria’s customers will be 70 or
less? (10 pts)
3. Explain to Illyria’s management why the probability that
the mean score of Vanchoc given by the simple random sample of
Illyria’s customers will be 70 or less differs for these two sample
sizes.