Statistics 121 Practice Test Exam 1

Questions and Answers

What will change the appearance of a histogram?

Changing the width of the intervals.

What type of plot is recommended for graphically displaying exam scores for 18 students ranging from 45% to 100%?

A stem & leaf plot.

Which one of the following variables is categorical?

Type of cell phone service (correct)

Height

Age

Weight

Which of the following variables is quantitative?

Number of students Signup and view all the answers

Which of the following is NOT a measure of center of the data?

Interquartile Range Signup and view all the answers

When the data are arranged in ascending numerical order, the median is the value which

Cuts the data in half. Signup and view all the answers

What does the five-number summary consist of?

Min, Q1, median, Q3, max. Signup and view all the answers

The standard Normal table can be used to find approximate percentages for any distribution that

Has an approximate Normal distribution. Signup and view all the answers

What can be concluded from the study about herbal tea?

The results are not convincing because the effect of herbal tea is confounded with the effect of visiting. Signup and view all the answers

If Joe's IQ score is 133, how many standard deviations is it above the mean (mean = 100, standard deviation = 15)?

2.2 Signup and view all the answers

What percentage of IQ scores are more than 2.5 standard deviations above the mean?

0.6% Signup and view all the answers

If the distribution of data is symmetric, then mean of the data _____ the median.

is = to Signup and view all the answers

What does standard deviation measure?

How much the observations in a data set vary about their mean. Signup and view all the answers

What is the difference between o- and s?

o- is the standard deviation of a population whereas s is the standard deviation of a sample. Signup and view all the answers

To standardize means to

Subtract the mean from a value and then divide by the standard deviation. Signup and view all the answers

Which one of the following is NOT affected by outliers?

Median Signup and view all the answers

What symbol should be used to represent the mean of 24 minutes?

lu Signup and view all the answers

What is the range for the middle 99.7% of the values of the normal curve?

30 Signup and view all the answers

What percentage of produced corks do NOT meet specifications if the mean is 3 cm and standard deviation is 0.1 cm?

31.74% Signup and view all the answers

Below what diameter are the smallest 10% of the corks?

2.872 cm Signup and view all the answers

How many standard deviations is a cork with a diameter of 3.135 cm above the mean?

12 Signup and view all the answers

Which one of the following does NOT have the same units of measure as the data?

z-score Signup and view all the answers

Why do we randomize in experiments?

To eliminate bias. Signup and view all the answers

What type of study is conducted when measuring sulfate levels and distance from a steel plant?

Observational study. Signup and view all the answers

What type of bias occurs when many selected individuals refuse to answer questions in a stratified sample?

Non-response bias. Signup and view all the answers

Two variables are confounded when

The effect of one variable on the response variable cannot be separated from the effects of another variable. Signup and view all the answers

Study Notes

Histogram Appearance

Changing the interval width alters the appearance of a histogram.

Data Representation

A stem-and-leaf plot is suitable for displaying exam scores of 18 students ranging from 45% to 100%.

Variable Types

Categorical variables include types of cell phone service.
Quantitative variables can be exemplified by weight.

Measures of Center

Interquartile range is not a measure of central tendency, unlike median and mean.

Median Definition

The median divides ordered data into two equal halves.

Five-Number Summary

Comprises minimum, first quartile (Q1), median, third quartile (Q3), and maximum.

Standard Normal Table

Useful for finding percentages in any distribution approximating a normal distribution.

Herbal Tea Study

The effectiveness of herbal tea cannot be conclusively determined due to the influence of visits on results.

IQ Test Scores

With a mean of 100 and a standard deviation of 15, a score of 133 is 2.2 standard deviations above the mean.
Only 0.6% of scores exceed 2.5 standard deviations above the mean.

Symmetric Distribution

In symmetric data distributions, the mean equals the median.

Standard Deviation Purpose

Measures the variation of observations around the mean.

Population vs. Sample Standard Deviation

Population standard deviation (σ) differs from sample standard deviation (s); both measure data variability.

Standardization Process

Involves adjusting a value by subtracting the mean and dividing by the standard deviation.

Outlier Influence

The median remains unaffected by outliers, in contrast to other measures.

Distribution of Test Completion Time

College freshmen’s test completion time has a mean of 24 minutes, represented by μ.

Range for Normal Curve Values

The range encompassing the middle 99.7% of normal curve values is 30.

Cork Manufacturing Specifications

Corks’ diameters are normally distributed with a mean of 3 cm and standard deviation of 0.1 cm; 31.74% do not meet specifications.

Diameter Percentiles

The smallest 10% of corks have diameters below 2.872 cm.

Standard Deviations Above Mean

A cork with a diameter of 3.135 cm is 12 standard deviations above the mean.

Measurement Consistency

A z-score does not share units of measure with the original data.

Randomization in Experiments

Randomization eliminates bias in experimental research.

Observational Study Definition

Analyzed sulfate levels at selected locations around a steel plant to observe the effect of distance on levels represents an observational study.

Non-Response Bias

When participants selected from a stratified sample refuse to respond, this results in non-response bias.

Confounded Variables

Two variables are considered confounded when the effect of one cannot be separated from the effect of the other.

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Description

Prepare for your Statistics 121 Exam 1 with this set of practice flashcards. Each card covers key concepts such as histogram appearance, graphing exam scores, and identifying categorical variables. Test your knowledge and improve your understanding of statistical concepts.