Exam 11: Statistics

Normal distributions are very commonly used for quality control in manufacturing. For example, a Manufacturer of light bulbs would surely be interested in studying how long their bulbs last. In one Case, the lifetime of one model of light bulb is normally distributed and has a mean X = 1,800 hours And a standard deviation of s = 250 hours. What percentage of bulbs would you expect to last longer Than 2,550 hours?

Assume that the finishing times for a group of runners in a marathon race are likely to be normally distributed. The mean finish time for male marathon runners is 288.46 min with a standard deviation of 39.7 min. The mean finish time for female marathon runners is 305.59 min with a standard deviation of 39.6 min. Would a male with a time of 128.62 minutes or a female with a time of 138.95 minutes finish faster relative to their gender? Explain why. (Remember that in a race you want to finish in a short time.)

A Z score tells you how many a data value is from the mean. Data values that are below the mean would have Z scores.

The grades on a college math exam are shown below. Construct a stem and leaf plot for the data.

Find the median.

Construct a bar graph for the number of stray animals in a certain city.

To find the arrange the data in order from smallest to largest. If the number of data values is odd, it will be one value in the middle of the ordered list. If the number of data values is even, it will be the mean of two middle values.

The average hourly wage of employees of a certain company is $11.15. Assume the variable is Normally distributed. If the standard deviation is $4.89, find the probability that a randomly selected Employee earns less than $7.97.

For the following data (a)Draw a scatter plot. (b)Find the value for r. (c)Test the significance of r at the 5% level and at the 1% level. (d)If r is significant, find the regression line and draw the line on the scatter plot. (e)Describe the nature of the relationship if one exists. (f)

Find the midrange.

The data below are the number of cattle on farms in the United States (in millions)for each year that Begins a decade from 1910 to 2010. Draw a box plot for the data below. Are there any outliers? If So, what are they?

Draw a bar graph illustrating the change in a state's tax rate on each of the axes below. Note that you'll be using the same information on each graph. Which of the two bar graphs would be used by someone wanting to argue that this tax cut will have a devastating effect on the state's budget? Why?

Select the graph below that best represents each description and fill in any blanks. A positive linear relationship exists when the points fall approximately in an ascending straight line from left to right. In this case as the x values are increasing, the y values are ________. This relationship is best illustrated by graph ________.

Which data set would be likely to have the larger standard deviation? EXPLAIN. Data set 1: Weights of all dogs at a golden retriever rescue shelter Data set 2: Weights of all dogs for sale in a pet store

The average hourly wage of employees of a certain company is $11.88. Assume the variable is normally distributed. If the standard deviation is $4.23, find the probability that a randomly selected employee earns more than $18.44.

Find the value for the correlation coefficient r.

These data represent the number of students attending a high school. Draw a time series graph for the data.

The following frequency distribution shows for a certain high school the number of freshmen, sophomores, juniors, and seniors who smoke. Construct a bar graph for the data.

Find the median.

Suppose that you find the mean weight of a group of dogs to be 62 pounds and calculate the standard deviation of the dogs weights to be 32.6. Carefully describe exactly what standard deviation tells you about the weights of the dogs.