Statistics Quiz on ANOVA and t-tests
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Questions and Answers

Which statistical test is appropriate when examining the difference between two groups with different participants per predictor level?

  • One-way repeated measures ANOVA
  • Factorial repeated measures ANOVA
  • Independent t-test (correct)
  • Dependent t-test

What research design requires the use of repeated measures ANOVA?

  • Using the same participants for each level of a predictor. (correct)
  • Examining relationships between variables in a multiple regression context
  • Examining the difference between two independent groups using interval data
  • Using different participants in multiple groups.

What is the key feature that distinguishes the use of an independent t-test from a dependent t-test?

  • The number of outcome variables.
  • Whether the participants are the same across groups. (correct)
  • The number of predictor variables.
  • The type of data being examined (nominal or ordinal).

Which statistical technique is best when analysing the relationship between multiple predictor variables, and a single outcome variable?

<p>Multiple Regression. (B)</p> Signup and view all the answers

When does a researcher use a factorial ANOVA?

<p>When assessing two or more predictor variables on a single outcome variable. (B)</p> Signup and view all the answers

A study comparing the effectiveness of three different teaching methods on student test scores, with each student only experiencing one method, would be best analyzed using which statistical approach?

<p>Independent ANOVA (C)</p> Signup and view all the answers

Which statistical technique is most appropriate when assessing the impact of height (measured in cm) and weight (measured in kg) on blood pressure (measured in mmHg)?

<p>Multiple regression (B)</p> Signup and view all the answers

A researcher wants to understand the effect of a new drug dosage (measured in milligrams) on reaction time. All participants are given all the dosage levels, in a randomized crossover design. Which statistical approach is most suitable?

<p>Dependent ANOVA (B)</p> Signup and view all the answers

If a statistical analysis involves a predictor variable with two levels (e.g., treatment vs. control), and the same participants are measured at both levels, what type of design is this classified as?

<p>Repeated Measures (B)</p> Signup and view all the answers

Suppose you are investigating the relationship between anxiety levels (measured on a continuous scale), type of therapy (cognitive behavioral therapy, psychodynamic therapy), and the number of sessions participants attend. What would be the best statistical test to analyze data from this study?

<p>Multiple regression (C)</p> Signup and view all the answers

Which condition in the analysis of variance (ANOVA) is not a core assumption that requires checking?

<p>That there is at least one statistically significant main effect (B)</p> Signup and view all the answers

If you are analyzing the impact of a treatment (categorized as either 'yes' or 'no') and age (in years, a continuous variable) on memory scores, and all participants only have the treatment level, what approach do you use?

<p>Multiple regression (D)</p> Signup and view all the answers

Which of the following is the key difference between independent and dependent ANOVA?

<p>Whether the groups being compared are related or independent (B)</p> Signup and view all the answers

What is the first step in calculating both the Wilcoxon rank sum and Mann-Whitney U statistics?

<p>Rank all data based on scores irrespective of the group. (A)</p> Signup and view all the answers

After ranking the data, what is the next step in calculating both Wilcoxon and Mann-Whitney statistics?

<p>Compute the sum of ranks for each group. (A)</p> Signup and view all the answers

What does the Wilcoxon statistic, WS, represent?

<p>The lower of the two sums of ranks. (B)</p> Signup and view all the answers

If two scores are tied, how are ranks assigned?

<p>The average of the ranks is assigned to both. (C)</p> Signup and view all the answers

In the context of the provided information, what would indicate little difference between the groups?

<p>The sums of their ranks would be similar. (D)</p> Signup and view all the answers

How is the Mann-Whitney U statistic calculated using the sum of ranks for group 1 (R1)?

<p>$U = n1n2 + n1(n2 + 1)/2 - R1$ (D)</p> Signup and view all the answers

What is the formula for calculating the mean of WS, the Wilcoxon statistic, given group sizes of n1 and n2?

<p>$WS = n1(n1 + n2 + 1)/2$ (B)</p> Signup and view all the answers

What is the formula for the standard error of WS (SEWS)?

<p>$SEWS = \sqrt{n1n2(n1 + n2 + 1)/12}$ (C)</p> Signup and view all the answers

If a study has two independent groups and the data does not meet the assumptions of parametric tests, which statistical test should be used?

<p>Mann-Whitney U test (C)</p> Signup and view all the answers

What is the appropriate statistical test to determine correlation between two variables where the data does not meet the assumptions of a parametric test?

<p>Spearman correlation (D)</p> Signup and view all the answers

For a study with one factor, measured repeatedly across multiple time points, where the data meets parametric assumptions, which test should be used?

<p>One-way repeated measures ANOVA (B)</p> Signup and view all the answers

When should a Wilcoxon signed-rank test be used?

<p>To compare two related groups with non-parametric data. (C)</p> Signup and view all the answers

What statistical test should be used when comparing three or more independent levels from a single factor and the data does not meet the assumptions of parametric tests?

<p>Kruskal-Wallis test (D)</p> Signup and view all the answers

Which statistical test should be used when the outcome is categorical and the data does not meet assumptions for parametric tests?

<p>Chi-Squared test (D)</p> Signup and view all the answers

If you have two factors being investigated, in an experimental design where both factors are manipulated and the data meets assumptions for parametric tests, what test should be used?

<p>Factorial ANOVA (A)</p> Signup and view all the answers

Which analysis is appropriate to analyze data from a study with a categorical dependent variable and multiple predictor variables, when parametric assumptions are not met?

<p>Logistic regression (B)</p> Signup and view all the answers

When comparing two related samples, and the assumptions for parametric tests are met, what is the appropriate statistical test?

<p>Paired t-test (C)</p> Signup and view all the answers

What statistical analysis is used in a study to account for a continuous variable influencing the outcome, while evaluating the effect of a single-factor manipulated independent variable on the same, continuous, dependent variable? Assume parametric assumptions are met.

<p>ANCOVA (C)</p> Signup and view all the answers

Which statistical test is appropriate for analyzing the relationship between two categorical variables?

<p>Chi-squared test (B)</p> Signup and view all the answers

If you have two independent groups and want to compare their medians, which test would be appropriate?

<p>Mann-Whitney test (A)</p> Signup and view all the answers

Which statistical approach is suitable when you have a categorical outcome variable?

<p>Logistic regression (C)</p> Signup and view all the answers

When you want to explore relationships between multiple categorical variables, which test is used?

<p>Log-linear analysis (A)</p> Signup and view all the answers

Which of these is a non-parametric test equivalent to a one-way ANOVA?

<p>Kruskal-Wallis test (A)</p> Signup and view all the answers

If you have three or more related groups and you want to compare their distributions, which non-parametric test should you use?

<p>Friedman test (C)</p> Signup and view all the answers

What test would you use to analyze the relationship between two continuous variables?

<p>Pearson correlation (D)</p> Signup and view all the answers

When you have the classic ANOVA assumptions but want to control for a continuous covariate, which statistical procedure would you use?

<p>ANCOVA (B)</p> Signup and view all the answers

In the context of the provided training data, what does the value '76' represent?

<p>The total number of cats that could dance (C)</p> Signup and view all the answers

What is the purpose of calculating row totals in the context of this example?

<p>To assess the proportion of dancing and non-dancing cats (A)</p> Signup and view all the answers

What do column totals represent in the contingency table given?

<p>The number of cats in each reward group, food or affection (A)</p> Signup and view all the answers

Based on the information provided, what does $F_{Efood,yes}$ represent?

<p>The expected frequency of cats that could dance when given food, under the null hypothesis (A)</p> Signup and view all the answers

What does 'N' represent in the formula $F_{Efood,yes} = \frac{RowTotal_{yes}}{N} \times ColumnTotal_{food}$ ?

<p>The total number of cats (B)</p> Signup and view all the answers

How is the expected frequency for a cell calculated under the null hypothesis?

<p>(Row total * Column total) / Total number of cats. (D)</p> Signup and view all the answers

What is the primary difference between the chi-square test ($\chi^2$) and the likelihood ratio test ($L\chi^2$) as presented?

<p>$\chi^2$ uses observed and expected values directly, while $L\chi^2$ uses logarithms. (C)</p> Signup and view all the answers

In the formula for the chi-square test, what does $\Sigma$ symbolize?

<p>The sum of all terms (B)</p> Signup and view all the answers

Given the formula $ \chi^2 = \sum \frac{(O_{Fij} - E_{Fij})^2}{E_{Fij}} $, what would happen if the observed frequency ($O_{Fij}$) was exactly equal to the expected frequency ($E_{Fij}$) in any given cell?

<p>That term would be zero (A)</p> Signup and view all the answers

How is the degrees of freedom (df) calculated in both chi-square and likelihood ratio tests?

<p>Using the formula (r-1)(c-1) where r is the number of rows, and c is the number of columns (C)</p> Signup and view all the answers

What is the null hypothesis in the context of this experiment?

<p>That there is no relationship between reward type and the ability to dance (A)</p> Signup and view all the answers

What is the first step in the presented decision tree?

<p>The decision tree information is not provided here. (D)</p> Signup and view all the answers

What is the expected frequency of 'no dancing with affection as a reward', based on the provided expected values (EXP) in the table?

<p>100.44 (D)</p> Signup and view all the answers

Within the chi-square formula as presented, what does the term $O_{Fij}$ represent?

<p>The observed number of cats in each cell. (A)</p> Signup and view all the answers

In the context of the likelihood ratio test, what is the function of ‘ln’?

<p>It calculates the natural logarithm. (C)</p> Signup and view all the answers

Flashcards

Continuous (CONT) variable

A type of measurement that is usually numeric and can take on any value within a range (e.g., height, weight, temperature).

Categorical (CAT) variable

A type of measurement that can only take on a limited number of values, often categories (e.g., gender, hair color, political affiliation).

One-way ANOVA

A statistical test used to compare means of two or more groups when the predictor variable has more than two levels.

Independent Samples t-test

A statistical test used to compare means of two groups when the predictor variable has two levels.

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Multiple regression

A statistical test that examines the relationship between two or more predictor variables and a continuous outcome variable.

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Repeated measures ANOVA

A statistical test used to compare means of more than two groups when participants are measured in the same condition multiple times.

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Paired Samples t-test

A statistical test used to compare means of two groups when the predictor variable has two levels and the participants are measured in both conditions.

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Two-way ANOVA

A statistical test that examines the relationship between two variables when the predictor variable has two levels or more.

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Paired Samples t-test (Dependent Samples t-test)

A statistical test used to compare the means of two dependent groups.

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Factorial ANOVA

A statistical test used to compare the means of two or more independent groups when there are two or more independent variables.

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Pearson Correlation

A statistical test used to examine the relationship between two continuous variables.

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Spearman Correlation

A statistical test used to examine the relationship between two ordinal variables.

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Mann-Whitney U Test

A non-parametric statistical test used to compare the means of two independent groups.

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Kruskal-Wallis Test

A non-parametric statistical test used to compare the means of three or more independent groups.

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Friedman Test

A non-parametric statistical test used to compare the means of three or more related groups.

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Wilcoxon Rank Sum Test

A statistical test used to compare the central tendency of two independent groups with ordinal data.

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Sum of Ranks

The sum of the ranks for all observations in a group.

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WS Statistic

The lower of the two sums of ranks calculated for the two groups in a Wilcoxon Rank Sum test.

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Mean of WS

A measure used in the Wilcoxon Rank Sum test that reflects the expected value of the WS statistic if there were no difference between the groups

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Standard Error of WS

A measure used in the Wilcoxon Rank Sum test which describes the variability of the WS statistic under the null hypothesis.

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Two Independent Conditions

A non-parametric test comparing two independent groups with ordinal data (like ranks).

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Average Rank

In any given rank, the average of the ranks assigned to tied scores.

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Chi-square test

A statistical test used to examine the relationship between two categorical variables. It determines if there is a significant association between the variables.

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Expected frequencies

The expected frequencies in a contingency table if there is no association between the variables.

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Residuals

The difference between the observed and expected frequencies.

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Null hypothesis

The null hypothesis in a chi-square test assumes that there is no association between the variables.

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Observed frequencies

The observed frequencies in a contingency table, representing the actual data collected.

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Alpha level

The statistical significance level used to determine if the observed frequencies are significantly different from the expected frequencies.

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Contingency table

A table that displays the frequencies of two or more categorical variables.

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Likelihood ratio test

A statistical test that focuses on the likelihood of observing the data if the null hypothesis is true.

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Decision tree

A data visualization tool that uses a tree-like structure to represent decisions and their outcomes.

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Degrees of freedom

The degree of freedom in a chi-square test is calculated as (r-1)(c-1), where r is the number of rows and c is the number of columns in the contingency table.

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Chi-square statistic

The formula used to calculate the chi-square statistic, involving the sum of squared differences between observed and expected frequencies divided by the expected frequencies.

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Proportion test

A statistical test used to compare the proportions of two or more groups, particularly when dealing with categorical data

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T-test

A statistical test used to examine the difference in means between two or more independent groups

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Correlation test

A statistical test that examines the relationship between two continuous variables.

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Main effect

The effect of a single independent variable on a dependent variable while controlling for other factors.

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ANCOVA

A statistical test used to compare means of two or more groups when you have a categorical (or grouping) variable with more than two levels and a continuous outcome variable. It's like a one-way ANOVA, but with the added complexity of controlling for the influence of another continuous variable.

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Wilcoxon Signed-Rank Test

A non-parametric test used to compare the medians of two related groups when the data is not normally distributed.

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Log-Linear Analysis

A statistical test used to analyze relationships between two or more categorical variables.

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Logistic Regression

A statistical technique used to analyze the relationship between a set of predictor variables (both categorical and continuous) and a categorical outcome variable.

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Study Notes

Research Design and Statistics: Non-Parametric Tests Overview

  • Categorical data analysis often uses chi-squared and likelihood ratio tests
  • Non-parametric tests are used when assumptions of parametric tests (e.g., normality) are not met
  • The Mann-Whitney U test compares two independent groups
  • Wilcoxon's signed-rank test compares two related groups
  • Kruskal-Wallis ANOVA on ranks compares multiple independent groups
  • Friedman's rank test compares multiple related groups

Categorical Outcomes: Chi-Squared Test

  • Participants are allocated to one category
  • Examples: pass/fail, pregnant/not pregnant, win/lose
  • Each participant's data contributes to the frequency of each category.
  • A table is used to display categorical frequencies (e.g., food or affection as training reward)
  • The test evaluates whether observed frequencies differ significantly from expected frequencies (under a null hypothesis).
  • Observed frequencies in a contingency table are compared with expected in similar circumstances
  • Calculation of expected frequencies using a formula is shown.

Categorical Outcomes: Likelihood Ratio

  • Preferred for small sample sizes
  • Similar to the chi-squared method, but uses a different formula to calculate the test statistic.

Comparing Two Independent Conditions: Wilcoxon Rank Sum Test (or Mann-Whitney U Test)

  • Two steps:
    • Rank all data regardless of group
    • Sum ranks for each group
  • Wilcoxon statistic (W) is the smaller of the two sums of ranks

Comparing Two Independent Conditions: Data Example

  • Data on BDI (Beck Depression Inventory scores) for participants taking alcohol or ecstasy on Sunday and Wednesday is provided.
  • Data is ranked to find whether depression scores differed, and whether drug type effects it

Wilcoxon sum of ranks - significance

  • The mean and standard error of the Wilcoxon sum of ranks (W) are calculated
  • A z-score is computed to determine Statistical significance of a result.
  • Two steps:
    • Compute the difference between scores for each participant across two conditions.
    • Rank the differences ignoring sign and exclude zero differences. Sum positive and negative ranks.

Wilcoxon Signed-Rank Test: Significance

  • The mean and standard error of the Wilcoxon signed-rank statistic are calculated
  • This allows for the computation of a z-score determining significance

Differences Between Several Independent Groups: Kruskal-Wallis Test

  • Two steps:
    • Rank all data regardless of group.
    • Calculate sum of ranks (Ráµ¢) for each group (áµ¢)
  • Statistic H is calculated using a formula in terms of the sample sizes and the Ráµ¢.
  • Two steps:
    • Rank each participant's scores for each condition; all data from all participants are ranked (no matter which group they belong)
    • Compute the sum of ranks for each condition (Ráµ¢)
  • The Friedman test statistic F is calculated.

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Test your knowledge of statistical methods, specifically focusing on ANOVA and t-tests. This quiz covers various scenarios including group comparisons and repeated measures designs. Perfect for students in statistics or research methods courses.

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