Knewton Alta - Chapter 1 Sampling and Data

explanatory variable (independent variable)

An explanatory variable explains or influences changes in another variable. In order to prove that the explanatory variable is the actual cause of the change in the response variable, it is necessary to isolate the explanatory variable.

Labels of weight status were added, such as under 18.5 = underweight, 18.5 to 24.9 = healthy, 25 to 29.9 = overweight, 30 or higher = obese. Which variables do these labels describe?

Explanatory The explanatory variable is the independent variable, which is the variable that is changed to determine its effect on a dependent variable. In this case, the explanatory variable is the BMI level.

Researchers are investigating whether taking aspirin regularly reduces the risk of heart attacks. Four hundred men participate in the study. The men are divided randomly into two groups: one group takes aspirin pills, and the other group takes placebo pills (a pill with no aspirin in it). The men each take one pill a day, and they do not know which group they are in. At the end of the study, researchers will count the number of men in each group who have had heart attacks.Identify the explanatory and response variables in this situation.

Explanatory variable: the type of pill the men took each day Response variable: whether a subject had a heart attack An explanatory variable explains or influences changes in another variable. The affected variable, the variable that is changed by altering the explanatory variable, is called the response variable. In an experiment, the researcher manipulates values of the explanatory variable and measures the resulting changes in the response variable.

True or False: The subjects are blinded in the study (above) by the Scent Company.

False Subjects will clearly know whether they can smell flowers or not, so subjects cannot be blinded in this study.

If the researcher decides to explore the role of gender in Vitamin D deficiency, what is the explanatory variable?

Gender The explanatory variable is the independent variable, which is the variable that is changed to determine its effect on a dependent variable. In this case, the explanatory variable is the gender.

A seed corn company keeps track of the daily temperature, in degrees Fahrenheit, of a field over the course of six weeks. What is the level of measurement of the data?

Interval This is interval data because degrees Fahrenheit is a numerical scale where differences are meaningful. However, because Fahrenheit does not have a true zero value, it is not ratio data.

What level of variables are "Start Date" and "End Date"? Date/time survey started Date/time survey completed

Interval Interval scale level - Data that is measured using this numerical scale has a definite order, and the differences between interval scale data can be measured. Since time of day does not have a true zero value, it is not ratio data.

A seed corn company keeps track of the daily temperature, in degrees Fahrenheit, of a field over the course of six weeks. What is the level of measurement of the data?

Interval This is interval data because degrees Fahrenheit is a numerical scale where differences are meaningful. However, because Fahrenheit does not have a true zero value, it is not ratio data.

A manager keeps track of the time of day that junior members leave work. What is the level of measurement of the data?

Interval This is interval data because time of day is a numerical scale where differences are meaningful. However, because the time of day does not have a true zero value, it is not ratio data.

A new mother keeps track of the time on a 12-hour clock when her baby wakes up each morning. What is the level of measurement of the data?

Interval This is interval data because time of day is a numerical scale where differences are meaningful. However, because the time of day on a 12 hour clock does not have a true zero value, it is not ratio data.

What level of variable is "Interact Pedestrian'?

Nominal Nominal scale level - Data that is measured using this scale is qualitative and not ordered

Looking at the dictionary for the survey about autonomous cars, what level of variable is "AV Safety Potential"?

Nominal Nominal scale level - Data that is measured using this scale is qualitative and not ordered.

Looking at the dictionary for the survey about autonomous cars, what level of variable is "AV Safety Potential"? Description or Question: Do you think that AVs have the potential to reduce injuries and fatalities Range of Responses: yes; maybe; no; not sure

Nominal Nominal scale level - Data that is measured using this scale is qualitative and not ordered.

A market researcher surveys households and asks what brand of shampoo is preferred. What is the level of measurement of the data?

Nominal This is nominal data because the brands of shampoo do not have an order to them. Even though a person may have a personal preference, there is no ranking that is universal.

In 2014, the website PhoneArena polled users, asking them which smartphone company had the best phone that year. The responses were the company names, such as Apple, Motorola, Nokia, Samsung, and Microsoft.Which of the following scale levels describes the data in this poll?

Nominal scale level This data should be measured with a nominal scale level, because data measured on this scale level cannot be ordered nor can it be used in calculations. This is just a list of phone companies, and there is no agreed upon order. Some people may favor Apple but that is a matter of opinion.

A market researcher surveys users of a certain laundry detergent if they think the detergent makes their laundry smell Very Bad, Bad, Neutral, Good, or Very Good. What is the level of measurement of the data?

Ordinal This is ordinal data because the values are ordered but do not have a meaningful numerical value.

A political researcher asks people if they Strongly Disagree, Disagree, Agree, or Strongly Agree with various policy decisions. What is the level of measurement of the data?

Ordinal This is ordinal data because the values are ordered but do not have a meaningful numerical value.

What level of variable is "AdvocacyIssues"?

Ordinal Ordinal scale level - Data that is measured using this scale can be ordered.

What level of variable is "PayingAttentionAV"?

Ordinal Ordinal scale level - Data that is measured using this scale can be ordered.

A hotel asks its patrons to fill out a customer satisfaction survey to rate the service. The options are Very Dissatisfied, Somewhat Dissatisfied, Somewhat Satisfied, Very Satisfied. What is the level of measurement of the data?

Ordinal This is ordinal data because the values are ordered but do not have a meaningful numerical value.

political researcher asks people if they Strongly Disagree, Disagree, Agree, or Strongly Agree with various policy decisions. What is the level of measurement of the data?

Ordinal This is ordinal data because the values are ordered but do not have a meaningful numerical value.

Which of the following scale levels would be best to measure the data - the heat ratings of different hot sauces - "hot," "hotter," "hottest"?

Ordinal scale level This data should be measured with an ordinal scale level, because data measured on this scale level can be ordered, but there is no way to use the responses in calculations. There would be no way to determine how much more heat "hottest" has than "hotter."

Which of the following scale levels would be best to measure the data - the heat ratings of different hot sauces - "hot," "hotter," "hottest"?

Ordinal scale level This data should be measured with an ordinal scale level, because data measured on this scale level can be ordered, but there is no way to use the responses in calculations. There would be no way to determine how much more heat "hottest" has than "hotter."

A track runner keeps track of how long it takes her to run the 200 meter dash. What is the level of measurement of the data?

Ratio This is ratio data because length of time has a true zero, and ratios are meaningful. If someone took twice as long to run the 200 meters, then that person ran half as fast.

If the survey asked for the number of pedestrians on any given day, what is the level of measurement?

Ratio Ratio scale level - Data that is measured using this scale addresses ratios and gives you the most information about the data. Ratio scale data is like interval scale data, but it has a starting point (also known as a "0 point") and ratios between the differences can be calculated.

A market researcher finds the price of several brands of cold medications. What is the level of measurement of the data?

Ratio This is ratio data because price has a true zero, and ratios of prices are meaningful.

response variable (dependent variable)

The affected variable, the variable that is changed by altering the explanatory variable, is called the response variable.

Response variable

The response variable is the dependent variable, which is the variable that is being measured or tested in response to changes in the independent variable

An established Scent Company conducted a study to investigate whether smell affects sleeping habits. Subjects were exposed to a floral smell wall plug-in while sleeping for 3 nights and 3 nights without. Participants were randomly assigned whether they would be exposed to the floral-scented during the first 3 nights or during the last 3 nights. Researchers found that participants slept longer during the nights with the floral-scented wall plug-ins than the nights without.Which of the following could be lurking variables in this study? Select all that apply.

The subject's impression of the floral scent - positive, neutral, or negative The strength of the subject's sense of smell The subject's age Explanation: This impression of the scent could be influencing the subject's sleep, if he or she does or does not like the floral scent of the wall plug-in. The strength of the subject's sense of smell could be influencing the subject's sleep, because a stronger sense of smell means the scent would affect the subject more. Age may affect how well the subject sleeps, so it is also a lurking variable.

The researcher found that overweight/obese controls had significantly lowered Vitamin D compared to normal weight individuals. What is the response variable in the study?

Vitamin D level The response variable is the dependent variable, which is the variable that is being measured or tested in response to changes in the independent variable

If the researcher decides to explore the role of gender in Vitamin D deficiency, what is the response variable?

Vitamin D level The response variable is the dependent variable, which is the variable that is being measured or tested in response to changes in the independent variable. In this case, the response variable is the Vitamin D level.

lurking variable

additional variables that can cloud a study

Margaret is investigating if gender has any effect on customer retention. What is the response variable?

customer retention The response variable is the dependent variable, which is the variable that is being measured or tested in response to changes in the independent variable. In this case the response variable is customer retention

Nominal Data

data of categories only. Data cannot be arranged in an ordering scheme. (Gender, Race, Religion)

Ratio Data

data with an absolute 0. Ratios are meaningful. (Length, Width, Weight, Distance) EX: Height, Age, Weight, Distance, Time

Interval data

differences between values can be found, but is NO absolute ZERO. Examples: SAT score, Date, IQ, Year, Temperature

A double-blind experiment

is one where both the subjects and the researchers are blinded.

Which of the following best describes the term explanatory variable?

the independent variable in an experiment An explanatory variable is defined as the independent variable in an experiment.

Ordinal

the values are ordered but do not have a meaningful numerical value.