PBSI 301 Exam IV Review

A sleep researcher collects data on the intensity of light in a room (in watts) and the time it takes participants to fall asleep (in minutes). The regressions equation is Y = 0.68X + 10.5. What does the slope (b) represent?

• A) For every 1-unit increase in light intensity, predicted time to fall asleep decreases by 10.5 minutes.

• B) For every 1-unit increase in light intensity, predicted time to fall asleep increases by 0.68 minutes.

• C) For every 1-unit increase in light intensity, predicted time to fall asleep increases by 10.5 minutes.

• D) The slope represents the starting point when X = 0.

Answer explanation

The slope (b = 0.68) indicates that for each additional watt of light intensity, the predicted time to fall asleep increases by 0.68 minutes.

A regression equation has an intercept (a) of 10.5. What does the intercept represent?

• A) The predicted time to fall asleep when light intensity is 0 watts.

• B) The point where the regression line crosses the Y-axis.

• C) The effect of light intensity on time to fall asleep.

• D) Both A and B

Answer explanation

The intercept is the predicted Y-value when X=0, which is 10.5 minutes. This is also the point where the regression line crosses the Y-axis.

A chi-square test is used to determine if there is a significant difference in preferences between three brands of yogurt. The obtained chi-square value is χ^2(2) = 4.46, p>0.05. What conclusion can be made?

• A) There is no significant difference in yogurt brand preferences.

• B) There is a significant difference in yogurt brand preferences.

• C) At least two of the brands are equally likely to be chosen.

• D) The chi-square test is not appropriate for this data.

Answer explanation

Since p>0.05, the result is not statistically significant, meaning there is no evidence of a difference in preferences between the yogurt brands.

In a factorial ANOVA, what does it mean if there is a significant interaction between factors A and B?

• A) At least one of the main effects must also be significant.

• B) Both of the main effects must also be significant.

• C) The effect of one factor depends on the level of the other factor.

• D) The interaction has no implications for the main effects.

Answer explanation

A significant interaction means that the effect of one independent variable depends on the level of the other independent variable.

For a sample of n = 16 what Pearson correlation is necessary to be statistically significant at α = 0.05 for a two-tailed test?

• A) 0.497

• B) 0.482

• C) 0.468

• D) 0.455

Answer explanation

Based on critical values of the correlation coefficient for n = 16, r ≥ 0.482 is required to achieve significance at α = 0.05.

What type of variables are required for a chi-square test?

• A) Continuous

• B) Categorical

• C) Criterion

• D) Both A and C

Answer explanation

Chi-square tests are used to analyze categorical data to determine if distributions differ from expected frequencies.

In a factorial ANOVA, an interaction effect indicates that the relationship between one factor and the dependent variable is constant across levels of the other factor.

• True

• False

Answer explanation

An interaction effect indicates that the relationship between one factor and the dependent variable changes depending on the level of the other factor.

The beta coefficient (b) in a regression equation can be used to determine whether the relationship between the predictor and outcome variable is statistically significant.

• True

• False

Answer explanation

Statistical significance is determined using t-tests or p-values, not the beta coefficient itself.

The Pearson correlation coefficient measures the strength and direction of the linear relationship between two continuous variables.

• True

• False

Answer explanation

The Pearson correlation assesses how well the relationship between two variables can be described by a straight line.

In a chi-square test, a larger obtained χ^2 value always indicates a stronger relationship between variables.

• True

• False

Answer explanation

The χ^2 value must be interpreted relative to the degrees of freedom and p-value.