# Probability: Normal Distribution and Null Hypothesis

**Topics:**Normal distribution, Standard deviation, Null hypothesis

**Pages:**2 (819 words)

**Published:**October 14, 2012

Woman| 101| 130| 30| 261|

Total| 163| 247| 90| 500|

What is the probability that: a. a randomly selected customer would pick the camera? 247/500= 0.494= 49.4%b. A randomly selected woman would pick the camera? 130/261=0.498=49.8%c. A randomly selected customer would be both male and choose the bike? 60/500=0.12=12% d. A randomly selected man would choose either the camera or the bike? 177/239=0.74=74% 2. a. Which part(s) of question 1 above deal with joint probability? C,b. Which part(s) deal with conditional probability? B,D The Standard Normal Curve 3. In a recent year, about two-thirds of U.S. households purchased ground coffee. Consider the annual ground coffee expenditures for households who purchase coffee, assuming that these expenditures are approximately normally distributed with a mean of $45.16 and a standard deviation of $10.00. a. Find the probability that a household spent less than $25.00. Z=(25-45.16)/10= -2.016 =.4778=2.2% b. Find the probability that a household spent more than $50.00 (50-45.16)/10=.484=18.44% c. What proportion of households spent between $30.00 and $40.00? 20.09% d. 99% of households spent less than what amount?15.16 4. The breaking strength of plastic bags used for packaging produce is normally distributed, with a mean of 5 pounds per square inch and a standard deviation of 1.5 pounds per square inch. What proportion of bags have a breaking strength of: a. less than 3.17 pounds per square inch?11.12% b. at least 3.6 pounds per square inch? 67.67 c. between 5 and 5.5 pounds per square inch?12.93%...

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