Statistics
Determine whether the statement is true or false. If it is false, rewrite it as a true statement. In a frequency distribution, the class width is the distance between the lower and upper limits of a class.
False. In a frequency distribution, the class width is the distance between the lower or upper limits of consecutive classes.
Questioning students as they leave a university parking lot, a researcher asks 387 students about their dating habits. What type of sampling is used?
Convenience sampling is used, because students are chosen due to convenience of location.
Skewed right if...
Dinosaur tail goes right
The method for selecting a stratified sample is to order a population in some way and then select members of the population at regular intervals.
False. The method for selecting a systematic sample is to order a population in some way and then select members of the population at regular intervals.
Using a systematic sample guarantees that members of each group within a population will be sampled.
False. Using a stratified sample guarantees that members of each group within a population will be sampled
Class Width =
Max - Min / #of classes Upper consec limit - Lower consec class limit (bar graph/ histogram)
Select all the levels of measurement for which data can be qualitative.
Nominal and ordinal
What is the difference between relative frequency and cumulative frequency?
Relative frequency of a class is the percentage of the data that falls in that class, while cumulative frequency of a class is the sum of the frequencies of that class and all previous classes.
Determine if the survey question is biased. If the question is biased, suggest a better wording. Why is walking every day good for you?
The question is biased. The wording "How do you think walking every day affects your health?" would be better.
Some quantitative data sets do not have medians.
The statement is false. All quantitative data set have medians.
A double-blind experiment is used to increase the placebo effect.
The statement is false. Double blinding is used to decrease the placebo effect.
Determine whether the following statement is true or false. If it is false, rewrite it as a true statement. The mean is the measure of central tendency most likely to be affected by an outlier.
The statement is true.
The midpoint of a class is the sum of its lower and upper limits divided by two.
The statement is true.
In a survey of 1155 adults in a country, 55% said the country's leader should release all medical information that might affect their ability to serve.
The study is observational, because it does not apply a treatment to the adults.
The most popular car color among the 35 residents of a retirement community.
The study is a census, because the population is small enough for it to be practical to record all of the responses
After constructing a relative frequency distribution summarizing IQ scores of college students, what should be the sum of the relative frequencies?
If percentages are used, the sum should be 100%. If proportions are used, the sum should be 1.
Select all the levels of measurement for which data can be quantitative.
ordinal, ratio, interval
A pharmaceutical company wants to test the effectiveness of a new allergy drug. The company identifies 250 females 30-35 years old who suffer from severe allergies. The subjects are randomly assigned into two groups. One group is given the new allergy drug and the other is given a placebo that looks exactly like the new allergy drug. After six months, the subjects' symptoms are studied and compared. Answer parts (a) through (c) below. (a) Identify the experimental units and treatments used in this experiment. Choose the correct answer below. (b) Identify a potential problem with the experiment design being used and suggest a way to improve it. Choose the correct answer below. (c) How could this experiment be designed to be a double-blind? Choose the correct answer below.
. The experimental units are the 30- to 35-year-old females being given the treatment. The treatment is the new allergy drug. There may be a bias on the part of the researcher if the researcher knows which patients were given the real drug. The study would be a double-blind study if both the researcher and the patient did not know which patient received the real drug or the placebo.
Use the row of numbers shown below to generate 12 random numbers between 01 and 99. 84068 06374 75735 01560 79430 59747 68215 85692
84 06 80 63 74 75 73 50 15 60 79 43
What is the difference between a frequency polygon and an ogive?
A frequency polygon displays class frequencies while an ogive displays cumulative frequencies.
Lower class limits = Upper class limits =
Class Width + minimum 1 (-) Second class
relative frequency =
Class frequency / sum of all frequencies
After a tornado, a disaster area is divided into 200 equal grids. Forty of the grids are selected, and every occupied household in the grid is interviewed to help focus relief efforts on what residents require the most.
Cluster sampling is used, since the disaster area is divided into grids, and some of those grids are selected and everyone in those grids is interviewed.
Chosen at random, 670 customers at a bank are contacted and asked their opinions of the service they received.
Simple random sampling is used, since the business is selecting from its customers at random, and all samples of 670 customers have an equal chance of being selected.
In 1965, researchers used random digit dialing to call 1300 people and ask what obstacles kept them from voting. What type of sampling was used?
Simple random sampling was used, since each number had an equal chance of being dialed, so all samples of 1300 phone numbers had an equal chance of being selected.
Carrots are planted on a 44-acre field. The field is divided into one-acre subplots. A sample is taken from each subplot to estimate the harvest. What type of sampling is used?
Stratified sampling is used, since the field is divided into subplots and a random sample is taken from each subplot.
Every fourth person entering a cafeteria is asked to choose his or her favorite meal from a list of five different meals that includes a description of each.
Systematic sampling is used, because every fourth person is selected.
How is a Pareto chart different from a standard vertical bar graph?
The bars are positioned in order of decreasing height with the tallest bar on the left.
Observational studies are sometimes referred to as natural experiments. Explain what this means.
n an observational study, a researcher measures characteristics of interest of a part of a population but does not change existing conditions.
A company has been rating television programs for more than 60 years. It uses several sampling procedures, but its main one is to track the viewing patterns of 20,000 households. These contain more than 45,000 people and are chosen to form a cross section of the overall population. The households represent various locations, ethnic groups, and income brackets. The data gathered from the sample of 20,000 households are used to draw inferences about the population of all households in the United States. Complete parts (a) and (b) below. What strata are used in the sample? Choose the correct answer below Why is it important to have a stratified sample for these ratings? Choose the correct answer below
The various locations, ethnic groups, and income brackets that are represented Stratified sampling ensures that each segment of the population is represented
Determine whether the statement is true or false. If it is false, rewrite it as a true statement. Class boundaries ensure that consecutive bars of a histogram touch.
True
What is the difference between a random sample and a simple random sample?
With a random sample, each individual has the same chance of being selected. With a simple random sample, all samples of the same size have the same chance of being selected.
Class boundaries =
difference between the lower and upper limit Half less than the result and subtract to lower classes Half more than the result and add to upper classes
approx. number =
highest point on graph
cumulative frequency =
sum of frequencies up to specific class
Which axis is the dependent axis?
y-axis
Determine if the survey question is biased. If the question is biased, suggest a better wording. How often do you eat vegetables during an average week?
No, because it does not lead the respondent to any particular answer
