Hello everybody, I am trying without much success to complete my A level
course work and I would be extremely appreciative and grateful if
anybody on the Allstat list would be kind enough to give up a few
minutes of their precious time to help me. I appreciate that your time
is very valuable so I will post the two types of problem with which I am
having difficulty with the hope that somebody will have the time to help
me. Yours hopefully, Bryan Jeanes, 17, Crosskeys College of F.E.
Newport, Gwent.
1. A local community was concerned about the speed of commercial traffic
in a residential area where the speed limit is set at 48km/h (30mph). A
survey showed that the average speed of commercial vehicles was 54km/h
and the standard deviation was 9.5km/h. The distribution of speeds
approximated that of the normal distribution.
(a) What percentage of commercial vehicles exceed the speed limit?
(b) What percentage of vehicles exceed 72km/h (45mph)?
(c) Between what speeds does the in interquartile range (the middle 50%)
fall?
2. A survey using a sample of 56 customers of a courier company revealed
that 72% were highly satisfied with the timing of their deliveries.
Using the 95% confidence interval, calculate the percentage range of the
population of customers who were highly satisfied.
(b) What sample size would be required to achieve a level of accuracy
within the population of plus or minus 3%?
I hope that somebody will be able to help, Cheers, Bryan.
PS, These are not the exact questions as I don't want the work done for
me , I just want worked answers to similar questions so that I can
follow the procedures and formulas to answer the actula problems on my
paper. To these ends I have posted two problems that are broadly similar
to the ones that I am having difficulty with. Thanks.
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