Stats Exam 1

A researcher is interested in the amount of time students spend on social networking sites. She obtains a sample of 10 students and records the amount of time (in minutes), in one day, they spend on Facebook, Instagram, or Twitter. Assume that the following summary information is from her data: N = 10, μ = 47.7, SS = 2000. What is the variance for this example?

200

Yolanda examined the GRE math scores of the second-year graduate students in her statistics class to see the variability. She found the variance to be 1600. What is the standard deviation?

40

A graduate statistics class is unhappy with midterm grades. The professor will curve the grades only if the class figures out how much the curve needs to be in order for the mean score to equal 85. What should the curve for the class be if these are the midterm scores for class members: 72, 88, 95, 76, 69, 71, 81, 80, 73, and 85?

6 points

Frances conducted an informal survey among the women living in her sorority house. One of the questions asked, "How many drinks do you have per week?" Frances found that the results for this question were negatively skewed. What does this mean?

Most women in the house drink a lot, but a few don't drink at all.

To compute the variance, the sum of the squared deviations is divided by:

N

Consider a study in which a group of people who drink an energy drink perform better during a mental alertness test than those who do not drink an energy drink regularly. What might be a possible confound in this study?

People who are regular energy drinkers may be naturally more mentally alert than those who are not.

What are raw scores?

Raw scores are the original data to which nothing has been done.

Yun wants to calculate the median in a set of scores, but there are two middle numbers. How should she determine the value of the median?

Report the average of the two middle scores.

A researcher studies the hours 2500 Canadians work out every week. Identify the sample and the population for this example.

Sample is 2500 Canadians who work out every week, population is all Canadians.

________ visually depict the relationship between two scale variables.

Scatterplots

Imagine that a researcher found that 70 percent of bystanders helped a female who couldn't start her car, but only 10 percent helped a male who couldn't start his car. What type of graph would be appropriate to display this data?

bar graph

A group of students graph the number of gold medals won by each country during the Olympics. What type of graph should they use and what should the y-axis include?

bar graph; the number of gold medals won

Suppose a researcher randomly assigns participants to one of three groups and examines their ability to solve complex mathematical problems under conditions of no noise, continuous noise, or random noise. What type of research design is the researcher using?

between-groups design

Lawrence is testing a series of new commercials on a sample audience for an advertising company. He wants to see which of 10 commercials receives the highest rating from audiences, but he wants to use a different audience for each commercial. What design should Lawrence use?

between-groups research design

Using someone's height as a measure of athletic ability is:

between-groups research design

Which of the following techniques for misleading with graphs involves using survey items that do not include the full range of possible responses—resulting in information that is slanted in a particular direction?

biased scale lie

The number of children in each family in a sample of 10 families is: 0, 0, 1, 1, 1, 2, 2, 2, 3, and 4. What type of distribution is this?

bimodal

The variable that is measured to determine if the independent variable had an effect is referred to as the ________ variable.

dependent

Statistical methods that organize and summarize groups of numerical data are classified as _____ statistics.

descriptive

Statistical methods that organize and summarize groups of numerical data are classified as ________ statistics.

descriptive

Which branch of statistics uses numerical observations and incorporates them into an organized and informative summary of the data?

descriptive

A researcher wants to learn about the vocabulary of two-year-olds. She measures the number of words for 300 two-year-olds. The average number of words for this group is an example of a:

descriptive statistic

When your professor announces the average exam score for your class, he is using:

descriptive statistics

A _______ effect occurs when some constraint prevents a variable from taking values below a certain point.

floor

When drawing a graph, the independent variable normally belongs on the:

horizontal x-axis.

A gun manufacturer publishes a graph indicating causes of death in a major city. The graph shows the number of people dying from gun violence in one column using a gun icon to represent every 100 deaths. A second column represents the number of people dying in car accidents, with each car representing a single death. This graph is attempting to mislead using the _____ lie.

inaccurate values

Using a graph to distort data—for example by changing graphics to emphasize one piece of information over another—would be an example of the _____ lie.

inaccurate values

Which of the following is typically manipulated by the researcher?

independent variable

The _______ variable predicts the _____ variable.

independent, dependent

Statistical methods that use sample data to draw inferences about larger populations are called ________ statistics.

inferential

If we rated attractiveness of celebrities on a scale from 1-5, the ratings would represent a(n) ___________ variable.

interval

A measure is said to be valid if:

it measures what it is supposed to measure.

A negatively skewed distribution has a long tail to the _____ of the distribution, while a positive skew has a long tail to the _____ of the distribution.

left; right

Suppose that, as part of a larger survey, we measure the variable "year in school." The variable has the possible values of freshman, sophomore, junior, or senior. These possible values are called:

levels or conditions

A frequency polygon is a:

line graph, with the x-axis representing values and the y-axis representing frequencies.

Outliers have the greatest effect on the:

mean

After grading all of her philosophy exams, Sylvia realizes that the distribution of scores is positively skewed. Which measure of central tendency would be most appropriate for Sylvia to use in this example?

median

If our data are nominal, we should use _____ as a measure of central tendency.

mode

When the bulk of data cluster together but trail off to the left, the skew is _____ ,when data trail off to the right, the skew is _____.

negative, positive

Identify the shape of the distribution of the following scores: 25, 26, 22, 27, 26, 26, 29, 30, 21, 22, and 4.

negatively skewed

A distribution containing a few extremely small values is likely to create a distribution that is:

negatively skewed.

If we asked 100 people how much they like pizza we would probably find that most people like it a lot with only a few people saying they don't like it at all. That is, the distribution of scores would be:

negatively skewed.

Using numbers to simply identify or label different objects or events involves _____ variables.

nominal

Bar graphs are used with _____ variables, while Pareto charts are used with _____ variables.

nominal; ordinal

A bar graph is appropriate if your independent variable is _____ and your dependent variable is _____.

nominal; scale

If the results from an intelligence test are different when the same person takes the test on two different occasions, the test is:

not reliable

Psychologists studying infant memory want to determine at what age babies can remember specific events. An experimenter uses several puppets to demonstrate a series of actions while the infant watches. After a delay, the experimenter records how many of the actions the child imitates when playing with the puppets. The dependent variable is the:

number of imitated actions

In a distribution that is positively skewed, most of the scores occur ______ of the distribution.

on the left side

In a research study it is important to specify exactly how we will measure the variables that will be studied. In other words, it is important that we use:

operational definitions.

If we asked 500 people how much they like spiders we would likely find a:

positive skew, with most people not liking spiders but a few liking them very much.

Because of their focus on controlling confounding variables, experiments that use between-groups research designs must use:

random assignment

If we made sure that each of our participants has an equal chance of being assigned to any condition in an experiment, we would be using:

random assignment

A private high school wants to show that students' test scores are superior to those of students in another school in the district. The administration creates a bar graph showing a very tall bar representing the private school's mean test score and a very low bar representing the mean score for the other school. What part of the graph would show if the private school is exaggerating the difference between schools?

range of values on the y-axis

Measuring a person's weight in pounds would involve using a(n) _____ variable.

ratio

The total number of females in a country is an example of which kind of variable?

ratio

A researcher wants to learn about the vocabulary of two-year-olds. She measures the number of words for 300 two-year-olds. The group of 300 is an example of a:

sample

A(n) _________ variable meets the criteria for either an interval variable or a ratio variable.

scale

Line graphs are similar to scatterplots in that they display the relation between two _____ variables, but line graphs can also represent _____.

scale; changes over time

A type of line graph that includes the line of best fit, which is used to make predictions for y variables on the basis of values of x, is based on a:

scatterplot

Michael wants to graph the relation between scores on the SAT and first semester grade point average in college. What type of graph should he use?

scatterplot

A _____ depicts the relation between two scale variables, whereas a _____ displays values of a scale variable within different categories of a nominal or ordinal variable.

scatterplot; bar graph

Imagine you saw a graph in the fictional magazine Metropolitan Woman that shows that over 50 percent of their married readers had an affair within the last year. You concluded correctly that the graph was misleading because readers of Metropolitan Woman are not necessarily representative of all married women. This is an example of the _____ lie.

sneaky sample

Which of the following techniques for misleading with graphs involves the selection of people to participate in a study so that the results turn out a certain way?

sneaky sample lie

Joline is a kindergarten teacher who is interested in calculating the variability in the number of sight words remembered by the 32 students in her class. What is the best measure of variability in this situation?

the standard deviation, because it uses all of the scores in the data set and is easy to interpret

A nurse at a local hospital records the number of male babies and the number of female babies born during the month of August. Should he create an ungrouped or grouped frequency table to represent the data?

ungrouped, because there are only two values on the x-axis

The number of forest fire fatalities in California for the last 10 seasons was reported as 3, 8, 3, 7, 7, 2, 8, 6, 2, and 3. What type of distribution is this?

unimodal

In a grouped frequency table how many intervals should you have?

usually between 5 and 10

When creating histograms and frequency polygons, the x-axis typically represents ______, while the y-axis represents _______.

values or intervals; frequencies

What is the difference between frequencies and grouped frequencies?

A frequency is a count of how many times a score appears. A grouped frequency is a count for a defined interval, or group, of scores.

What is the difference between a histogram and a bar graph?

Bar graphs typically provide scores for nominal data, histograms typically provide frequencies for scale data. Also, categories in bar graphs do not need to be arranged in a particular order and the bars should not touch. Intervals in histograms are arranged in a meaningful order (LOWEST to HIGHEST) and bars should TOUCH.

Which are used in inferential statistics: samples or populations?

Data from samples are used in inferential statistics to make an inference about the larger population.

If your professor calculated the average grade for your statistics class, would that be considered a descriptive statistic or an inferential statistic?

Descriptive statistic because it's being used only to describe the tendency of people in your class with respect to a statistics grade.

What is the difference between descriptive statistics and inferential statistics?

Descriptive statistics organize, summarize, and communicate a group of numerical observations. Inferential statistics use a sample data to make general estimates about the larger population.

What is the difference between discrete observations and continuous observations?

Discrete observations can take on only specific values, usually whole numbers. Continuous. observations can take on a whole range of values.

Distinguish between discrete and continuous variables.

Discrete variables can only be represented by specific numbers, usually whole numbers. Continuous variables can take on any value, including those with decimal precision.

Which of these is a step for creating a frequency polygon from a grouped frequency table but NOT from a standard frequency table?

Find the midpoint for every interval.

Why is it sometimes easier to use a frequency table to interpret data than to examine a distribution of raw scores?

Frequency tables display patterns, organizing the data by how often each score occurs.

What is the main difference between a between-groups research design and a within-groups research design?

In a within-groups research design, the participants experience all conditions of the experiment.

What is the primary difference between descriptive and inferential statistics?

Inferential statistics allow researchers to draw conclusions about populations while descriptive statistics simply organize and summarize data.

"The Most Misleading Graph Ever Published," discussed in your text, indicates that Cornell University's quality of education declined in recent years. In what way is this misleading?

The graph was misleading because Cornell's education ranking actually improved from 15th to 6th, but the declining line on the graph implied that quality of education was getting worse.

A researcher is interested in the effects of sleep deprivation on memory. Assume that memory (the dependent variable) is always measured the same way—as the number of items recalled on a standard memory test (i.e., this is a scale variable). However, the independent variable could be manipulated in a number of different ways. For which of the options below would a line graph or scatterplot be most appropriate?

The researcher records the number of hours that each person sleeps.

Suppose you notice in a graph titled "Changes in Happiness Across the Lifespan" that levels of happiness seem to decline with age. When you read more about the study, however, you learn that "happiness" was only measured at two points in time, at 20 years and 80 years. You feel that the number of times the measurement was taken might be misleading and that this graph could display:

an interpolation lie.

If we were interested in studying the effect of drug abuse on employment we would probably use a(n) _____ study because of ethical issues involved in employing random assignment.

correlational

Any unnecessary, distracting information on a graph can be referred to as:

chartjunk

The symbol SS stands for:

sum of squared deviations.

Identify the shape of the distribution of the following scores: 6, 7, 7, 12, 17, 17, and 18.

symmetrical

Which one of these is an interval variable but not a ratio variable?

temperature

A researcher observed that children playing violent video games were more aggressive than those who did not play violent video games. For this study, what is the dependent variable?

the level of aggression displayed by the children

In computing variance and standard deviation we are interested in how much individual scores vary from:

the mean.

Professor Gomez designs a study to assess the role of imagination inflation on the development of false memories. Research participants are given a number of simple tasks (e.g., tapping a pencil or bouncing a ball) that they will either perform or simply imagine performing. Later their memory of whether or not they performed the task will be assessed. If graphing the results of this study, where should we place the memory scores?

vertical y axis

The standard deviation of a population is symbolized by:

σ.