Stats Review

Ana wants to know the average student’s opinion of the tardy policy at her school. Which group of students should she survey in order to achieve the most accurate results?

• thirty students who are often tardy
• thirty students who are rarely tardy
• thirty of her friends
• thirty randomly selected students from her school

Can pleasant aromas help a student learn better? Two researchers believed that the presence of a floral scent could improve a person’s learning ability in certain situations. They had 22 people work through a pencil-and-paper maze six times, three times while wearing a floral-scented mask and three times wearing an unscented mask. The three trials for each mask closely followed one another. Testers measured the length of time it took subjects to complete each of the six trials. They reported that, on average, subjects wearing the floral-scented mask completed the maze more quickly than those wearing the unscented mask, although the difference was not statistically significant. This study is

• a convenience sample 
• an observational study, not an experiment
• an experiment

• a double-blind experiment

An amateur gardener decides to change varieties of tomatoes for this year to see if the yield is improved. He puts 6 of the old type of tomato plants and 6 of the new tomato plants in his garden. The average yield for the old plants was 11.3 pounds and the average for the new plants was 14.5 pounds. This is an example of

• an experiment
• an observational study

210 college students were randomly assigned to play either a violent or nonviolent video game.  A short time later, the students were presented with the opportunity to trivially harm another person and results comparing the two groups were recorded.
Is this study OBSERVATIONAL or EXPERIMENTAL? 

• Observational
• Experimental

A study is conducted to investigate the relationship between owning pets and happiness. 100 subjects are randomly selected and data on whether or not a pet is owned and a happiness score (1‐10, 10 being extremely happy) are obtained.
Is this an OBSERVATIONAL or EXPERIMENTAL study?

• Observational
• Experimental

The Empirical (68-95-99.7) Rule can be applied only if data is ....

• Normally Distributed

• Uniform

• Skewed

• Symmetric

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

Which interval shows 95% of the data given a mean of 15 and a standard deviation of 3? 

• 9 to 21
• 12 to 18
• 6 to 24
• 13 to 16

According to the empirical rule, what percentage of data falls within 1 standard deviation? 

• 25%
• 68%
• 95%
• 99.7%

According to the empirical rule, how much of the data falls within 3 standard deviations? 

• 25%
• 68%
• 95%
• 99.7%