Intro to Stats

If a number is added to a set that is far away from the mean, how does this affect standard deviation?

• increase
• decrease
• stay the same
• both increase and decrease

If a number is added to the set that is in the middle of the data, how does this affect the range?

• increase
• decrease
• stay the same
• both increase and decrease

1.  Which best describes the shaded part of this normal distribution graph?  

• All data that is one or higher.
• All data that is one or more standard deviations above the mean.
• All data that is between 1 and 3.
• All data that is above the mean.

What shape is a normal distribution curve?

• Half curve
• Round curve
• Bell curve
• Square curve

The mean life of a tire is 30,000 km. The standard deviation is 2000 km.

Then, 68% of all tires will have a life between ___________ km and __________ km.

•  28,000 km and 32,000 km.
• 24,000 km and 34,000 km.
• 26,000 km and 34,000 km.
• 27,000 km and 31,000 km.

Between what two standard deviations of a normal distribution contain 68% of the data?

• one below and one above
• two below and two above
• two below and zero
• zero and two above

The distances male long jumpers for State College jump are approximately normal with a mean of 263 inches and a standard deviation of 14 inches.  
Suppose a male long jumper's jump ranked in the 75th percentile.  How long was his jump?

• 0.67 inch
• 263 inches
• 272.44 inches
• 277.25 inches

The z-score represents.....

• the amount of standard deviations a data value is above or below the mean.
• the percentile the data value is above or below the mean.
• the amount of standard deviations a data value is above or below the median.
• the percent the data value is above or below the mean.

Here is the dot plot of voter turnout (as a percentage of voting-age population) for the 50 states—plus the District of Columbia—in a recent presidential election. Which of the following best describes this distribution?

• The distribution of voter turnout is skewed slightly left, centered at about 62%, with a range of 24%.
• The distribution of voter turnout is roughly symmetric, centered at about 60%, with a range of 30%.
• The distribution of voter turnout is skewed slightly right, centered at about 62%, with a range of 24%.
• The distribution of voter turnout is bimodal, centered at about 60%, with a range of 30%.

The stem-and-leaf diagram below gives the distribution of the ages in years of 20 participants at a family reunion. Which of the following statements about the distribution is correct?

• The first quartile is larger than the third quartile.
• The distribution is strongly skewed to the left.
• It makes the most sense to use the mean and standard deviation as a numerical summary of the center and spread of this distribution.
• The mean is larger than the median.