Statistics

How many scores are between 40 and 50?

4 , There are four scores with a stem of four: 44, 47, 48, and 49

In a study of the effect of handedness on athletic ability, participants were divided into three groups: right-handed, left-handed, and ambidextrous. Athletic ability was measured on a 12-point scale. The dependent variable is

Athletic ability is the dependent variable.

A random sample

sample used most frequently by social scientists every person in the target population has an equal chance of being selected.

Two basic divisions of statistics are inferential and descriptive.population and sample. sampling and scaling. mean and median

the two divisions of statistics are inferential and descriptive.

The smallest value is

-2.8 The stems are multiplied by one, so the lowest is (1)(-2) - 0.8. Note that with negative stems, the leaves are subtracted.

Variable

A factor that can change in an experiment

Stem and leaf displays are good for comparing two groups. True False

True Back-to-back stem and leaf displays are good for comparing two groups.

A random sample is one

which every sample of a particular size has an equal probability of being selected.

Three-dimensional bar charts make it easier to interpret the data. true or false.

In general, it is a bad idea to have more display dimensions than data dimensions. Three-dimensional bar charts are not as clear as two-dimensional bar charts.

The independent variable is _________; the number of levels of the independent variable is _______.

handedness; three The independent variable is handedness. Since there are three types of handedness, the number of levels is 3.

Inferential Statistics

procedures used to draw conclusions about larger populations from small samples of data

Although bar charts are often used to show means, this text recommends that _________ be used instead.

box plots Box plots contain more information and take up less space. They are therefore preferable to bar charts.

When you have relatively few observations you should use percentages rather than frequencies. true or false

false , Percentages can be misleading when you have relatively few observations. They can make a small difference look large.

The highest value in the data set multiply stems by 10 plus 2

132 The highest value is 132. You multiply the stem by 10 and add the leaf. For the highest value, this is (10)(13) + 2.

A frequency polygon is very similar to a

Histogram, Frequency polygons do not list the raw data, as stem and leaf plots do. Frequency polygons are very similar to histograms, except histograms have bars and frequency polygons have dots and lines connecting the frequencies of each class interval.

Inferential Statistics 2

Populations and samples In statistics, we often rely on a sample --- that is, a small subset of a larger set of data --- to draw inferences about the larger set. The larger set is known as the population from which the sample is drawn.

Which of the following are qualitative variables?

The qualitative variables are hair color and gender.

What is the upper hinge?

The upper hinge is the 75th percentile. It is the top of the box.

Check all that apply. Frequency polygons are better than histograms for:

comparing distributions Frequency polygons are better at comparing distributions because two frequency polygons can be displayed in the same graph without obscuring each other. Both histograms and frequency polygons show the shape of the distribution. Neither necessarily reveals the exact values in a distribution.

What's the upper adjacent value

Upper adjacent value. It is the largest value below the upper inner fence which is one step above the upper hinge.

Suppose that your data include 4000 observations, and you must choose the number of intervals to represent in your histogram. What does Sturges' rule recommend?

According to Sturges' rule, there should be 13 intervals because the base 2 logarithm of 4096 (which is close to 4000) is 12. Thirteen intervals. Sturges' rule sets the number of intervals as close as possible to 1 + Log2(N), where Log2(N) is the base 2 log of the number of observations.

Bar charts can only be used for qualitative variables. True or False

Although bar charts can be used for qualitative variables, they can also portray quantitative variables.

Higher rates of ice cream consumption and drowning for a city correspond. This leads people to believe that eating ice cream can somehow put you at risk of drowning. Can you think of another interpretation?

Yes,There is a third variable involved here--the summer. More people eat ice cream in the summer and more people swim in the summer.

What should you take into consideration when evaluating statistical claims? Check all that apply. The statistics presented The sources of the statistical findings The procedures used to generate the claims

As opposed to just accepting numbers or findings, you should think about all of these things when evaluating a statistical claim. The statistics presented The sources of the statistical findings The procedures used to generate the claims

what statistics would provide the location of the fulcrum at which the distribution would be in balance?

The mean, median and mode are all the same for this distribution and would balance the distribution.

Extreme scores are shown with the letter o.

false Values outside the "outer fences" are always shown with an "*". Values outside the inner fences but within the inner fences are shown with an "o".

Descriptive statistics

Descriptive statistics summarize and describe data. Inferential statistics use data from a sample to answer questions about a population. Inferential statistics involves generalizing beyond the data at hand.

What does the "bin width" of a histogram refer to? The range of scores after allowing for some "padding." The average class frequency. A measure of "distribution skew".

The size of each class interval. Bin width is another name for the width of each class interval.

The variable athletic ability is

The variable is discrete because the rating scale contains only 12 points and therefore is not continuous. Athletic ability is a discrete quantitative dependent variable.

You hear in a commercial that 80% of children prefer to eat a certain kind of cereal for breakfast. What do you conclude? This cereal is superior to all others...at least according to kids. You need to know more about where these data came from before making any conclusions. 20% of kids prefer to eat Trix.

To be an intelligent consumer of statistics, your first reflex must be to question the statistics that you encounter.

A box plot always indicates the highest and lowest values.

True .If the highest value is an outside (or far out) value then it is indicated by an "o" (or an "*"). If highest value is not an outside value then then it is indicated by the top of the higher whisker (the upper adjacent value). The same goes for the lowest value.

Dot plots are typically used to represent frequencies. True or False

True / Although dot plots could be used to represent statistics such as means, it is not recommended. They are typically used for frequencies.

When participants who arrive for a research study are put into treatment groups on the basis of chance,

random assignment has occurred. Random assignment has occurred because the decision as to which subject goes into which group is random.

Line graphs should be avoided when

the variable on the X-axis is a qualitative variable. Line graphs should not be used with a qualitative variable because line graphs are designed to show trends.

Box plots are preferable to stem and leaf displays when

there is a large amount of data. three or more groups are to be compared. The two correct choices are (1) there is a large amount of data and (3) when more than two groups are compared. Stem and leaf displays show individual values and skew well.

A biased sample is one that

will likely have groups from the population over-represented or under-represented due to systematic sampling factors. Only when the sampling is systematically favoring one group or another is the sample biased. Random samples, although they can be different from the population, are not biased. Bias is defined by the procedure for drawing the sample, not by the result.

Pie charts and bar charts can both be effective methods of portraying qualitative data.

Bar charts are better when there are more than just a few categories

Stem and leaf displays are good for comparing three groups. True False

False Stem and leaf displays are not well suited for comparing three or more groups.

When there are many categories, it is best to use a pie chart., horizontal bar chart. or vertical bar chart.

Horizontal bar charts are usually better than vertical bar charts because there is more room to label the categories. Pie charts are not good for displaying many categories.

Which of the following are part(s) of statistics? Select all that apply. numerical calculations, graphs interpretations and decisions based on the numbers and graphs

Statistics is a field of study concerned with summarizing data, interpreting data, and making decisions based on data. It involves all of those things.

A stem and leaf display is a good method of displaying large amounts of data. True False

Stem and leaf displays can be unwieldy with large amounts of data because every single data value is shown in the figure.

The H-spread is:

The H-spread is the difference between the upper hinge (D) and the lower hinge (G).

In an experiment on the effect of sleep on memory, the dependent variable is

The dependent variable is the recall score on a memory test.

In an experiment on the effect of sleep on memory, the independent variable is

The independent variable is the number of hours of sleep.

Which of the following is/are true?

The lowest value is H. There is an outside value, but no far out value.

Which of the following are descriptive statistics?

The mean age of people in Detroit. The number of people who watched the superbowl in the year 2002. The median price of new homes sold in Miami. The height of the tallest woman in the world.

What is the median?

The median is represented by a line through the middle of the box.

Which of the following is (are) true? Using a random sample is to accept some uncertainty about the conclusions. enables you to calculate statistics. is to risk drawing the wrong conclusions about the population. biases your results.

is to accept some uncertainty about the conclusions. enables you to calculate statistics. is to risk drawing the wrong conclusions about the population. Random sampling does not produce bias, which means systematic rather than random error.

Uncertainty regarding conclusions about a population can be eliminated if you

obtain data from all members of the population. The only way to eliminate uncertainty is to obtain data from the whole population. You can reduce uncertainty with a large sample.

Our data come from _______, but we really care most about ______.

samples; populations

The largest value is: Multiply Stems by 1.0

6 The stems are multiplied by one, so the highest is (1)(6) + 0.0.

A qualitative variable is sometimes measured on a continuous scale., a categorical variable., a numeric variable.

A categorical or qualitative variable is one in which responses are classified according to which category they are in. There is no numeric ranking of the categories.

Line graphs are most similar to bar charts.

A line graph is a bar graph with the tops of the bars represented by points joined by lines.

A graph with a large lie factor omits data that do not fit the hypothesis. is distorted because the baseline is not zero. greatly exaggerates differences by comparing areas instead of heights.

Although all of these choices refer to misleading ways that graphs can be constructed, the term "lie factor" refers to the ratio of the size of the effect shown in a graph to the size of the effect shown in the data. When relevant pictures, as opposed to simple bars, are used in graphs, the heights of these pictures may accurately portray the data, but their area differences could be extremely misleading.

Response times were generally shorter to the large target or small target

Larger target, Almost all of the times for the large target are below 750 msec., whereas there are many longer times for the small target.

Which of the following is a random sample of a college student body?

Lisa Meyer, Todd Jones, and Maria Rivera, whose ID numbers were picked from a table of random numbers.