Sampling and Data
A political scientist surveys 40 of the current 119 representatives in a state's legislature. What is the size of the sample?
40
Which of the following is a quantitative variable?
- Phone Number
- Number on a football player's jersey,
- Student ID Number
- Number of Siblings
Number of siblings.
Based on a survey of 1,780 students, Dave found that 16% of students used public transportation. How reliable is this result and why?
Very reliable because 1,780 is a very large sample.
A ping pong ball is drawn at random from an urn consisting of balls numbered 2 through 10. A player wins 1 dollar if the number on the ball is odd and loses 1 dollar if the number is even. What is the expected value of his winnings? Round to the nearest cent.
Is this value from a discrete or continuous data set.
The average rainfall in July in inches
Continous
You work for a company as a quality control specialist. You want to check the current production of products for defects. Your factory has 5 different assembly lines. At the end of the day, you visit each assembly line and randomly choose four items to inspect. What type of technique was used to sample?
Stratified Random Sample
In a study, the data you collect is Favorite candy bar.
What is the level of measurement?
Nominal
Slide 4 on PowerPoint
B
When an opinion poll calls a residential telephone number at random, there is only a 20% chance that the call reaches a live person. You watch the random digit dialing machine make 15 calls. Let X = the number of calls that reach a live person.
Yes, we have a fixed number of observations. It is reasonable to believe that each call is independent of the others, 'Success' means reaching a live person while 'failure' is any other outcome, and each randomly dialed number has chance p = 0.2 o reaching a live person.
Slide 7 of PowerPoint
.47
Use a calculator to find a simple random sample of 4 numbers, 1-30. Use a seed value of 120.
13, 6, 19, (19) 8
Slide 1 on PowerPoint
Conditional Probability
Slide 5 on PowerPoint
6/48
A baseball player has a batting average of 0.245. What is the probability that he has exactly 1 hits in his next 7 at bats? Round your answer to four decimal places.
.3176
3, 22.2, 24.1, 32.4, 34.6, 43.8, 52.6, 52.7, 59.1, 67
Find the 27th percentile of the data shown.
24.1
The prices of generic items are compared to the prices of the equivalent named brand items. Are the two samples matched pairs or not? Why or why not?
Yes. The same item is used in each sample. The differences between prices of items can be found.
Slide 2 on PowerPoint
2
A survey of athletes at a high school is conducted, and the following facts are discovered:
An athlete is chosen at random from the high school. What is the probability that the athlete is a football player or a basketball player?
87%
According to the American Red Cross, 10% of all Connecticut residents have Type B blood. A random sample of 23 Connecticut residents is taken.
X=the number of CT residents that have Type B blood, of the 23 sampled.
What is the standard deviation of the random variable X?
√2.07
Slide 8 on PowerPoint
-0.66
A researcher wants to determine if diet and exercise together helps people lose weight over just exercising. The researcher solicits volunteers to be part of the study, randomly picks which volunteers are in the study, and then lets each volunteer decide if they want to be in the diet and exercise group or the exercise only group. Is this a randomized experiment? Why or why not?
No. The subjects choose which group to be in.
Slide 3 on PowerPoint
False
Slide 6 on PowerPoint
.5
21.3% of flowers of a certain species bloom "early" (before May 1st). You work for an arboretum and have a display of these flowers.
In a row of flowers, what is the probability that you will have to observe 6 flowers in order to see the first one that blooms early?
0.064306261944487
The heights of adult men in America are normally distributed, with a mean of 69.5 inches and a standard deviation of 2.67 inches. The heights of adult women in America are also normally distributed, but with a mean of 64.4 inches and a standard deviation of 2.56 inches.
If a man is 6 feet 3 inches tall, what is his z-score (to two decimal places)?
2.06