Stats Lab Exam 1 Review

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Questions and Answers

What kind of variable is a student's GPA?

Categorical
Dependent
Quantitative (correct)
Independent

What is the standard deviation of a dataset with a variance of 16?

4 (correct)
8
256
None of the above

What type of graph would be most appropriate to display the frequency of different hair colors in a sample of 100 people?

Line graph
Scatterplot
Histogram
Bar chart (correct)

What is the skewness of a distribution with a skewness statistic of -1.5 and a skewness standard error of 0.3?

Negatively skewed (D)

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If the p-value of a one-sample t-test is 0.01, what conclusion can we draw?

The null hypothesis is rejected (C)

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A researcher wants to test if the average height of women is different from 5'4". What are the null and alternative hypotheses?

H0: µ = 5'4"; H1: µ ≠ 5'4" (C)

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What is the purpose of a one-sample t-test?

To compare a sample mean to a known population mean (D)

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Which of the following is NOT a characteristic of a normal distribution?

Tails extend indefinitely in both directions (C)

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What is the appropriate statistical test to use when comparing a sample mean to a known population mean?

One-sample t-test (A)

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Which of the following is NOT a step involved in performing a one-sample t-test in SPSS?

Calculate the mean and standard deviation of the sample (B)

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When presenting the results of a one-sample t-test in APA style, what three values are required?

t-statistic, degrees of freedom, p-value (B)

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What does a p-value less than .05 indicate in a one-sample t-test?

The sample mean is significantly different from the population mean. (D)

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What is the null hypothesis for a one-sample t-test?

The sample mean is equal to the population mean. (C)

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Flashcards

Rejecting the null hypothesis

Deciding to reject the null hypothesis when p < .05 in SPSS output.

Recode age groups

Transform continuous age data into categorical values (e.g., 18-25 = 1).

One sample t-test reporting

Report t value, degrees of freedom (df), and p value in APA style.

Nominal variables

Categorical variables without a numeric value (e.g., gender).

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Skewness

A measure of the asymmetry of a probability distribution (e.g., positive skew).

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Interval Variable

Numerical variables with meaningful quantitative differences.

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Dependent Variable

A variable thought to be a result of another variable.

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Mean

The sum of values divided by the number of values in a group.

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Standard Deviation

A statistic that measures the average variability of a dataset.

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Null Hypothesis

The hypothesis stating there is no effect or difference; used in hypothesis testing.

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Outlier

A data point that significantly differs from other observations.

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Study Notes

Variables

Nominal variables have categories without quantitative differences.
Scale variables describe numerical variables with meaningful differences.
A dependent variable is a result of another variable.
An independent variable causes an effect.
Examples of categorical variables include religious affiliation and letter grades.

Descriptive Statistics

The mean is the sum of all numbers divided by the count.
Variability, or spread, of the data can be estimated via standard deviation.
In SPSS, use the AVERAGE function to calculate the average of multiple variables.
In SPSS, use the Analyze > Descriptive Statistics > Frequencies menu to get descriptive statistics.
Standard deviation squared is variance.

Graphing

The image is a bar graph.
A bar graph visually displays categories and their respective values.
The dependent variable on a bar graph goes on the y-axis or vertical axis.

Old Faithful Eruptions

The graph shows the relationship between eruption duration and waiting time.
The graph is a scatter plot, displaying data points as (x, y) coordinates.
The line on the scatter plot is the linear regression line.

Skew and Kurtosis

Skewness describes the asymmetry of a distribution.
Kurtosis measures the "tailedness" or peak of a distribution.
A normal distribution is symmetrical with a kurtosis of 3.

One Sample t-tests

In a one-sample t-test, the sample mean is compared to a population mean.
Statistical significance is typically defined as a p-value less than 0.05.
If p is equal to or less than 0.05, the null hypothesis is rejected.
The null hypothesis is rejected when the p value is less than 0.05.
A one sample t-test in SPSS utilizes 'Analyze' > 'Compare Means' > 'One-Sample T Test'. The input value is the population mean value.

Miscellaneous

Box plots, often called box-and-whisker plots, display data distribution.
The p-value is the criterion for rejecting the null hypothesis.
To recode a variable in SPSS, use the Transform > Recode into Different Variables menu.
For APA style, the output values for a one-sample t-test include the t statistic, degrees of freedom, and p-value.