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WGU Statistics
Test SOLUTION
A clinical trial designed to evaluate the efficacy of a new drug to increase HDL cholesterol is conducted. One hundred patients enroll in the study and are randomized to receive either a new drug or a placebo. A multiple regression analysis is used to assess effect modification. Let T = Treatment (1 = new drug, 0 = placebo), M = male gender (1 = Yes, 0 = No), and TM = the interaction of treatment and male gender. Given the following results: Independent variable Regression coefficient T p-value Intercept 39.24 65.89 0. T(Treatment) -0.36 -0.43 0. M(Male) -0.18 -0.13 0. TM(Treatment X Male) 6.55 3.37 0. What is the linear regression model?
T = 65.89 - 0.13(M) + 3.37(TM)
HDL = 39.24 - 0.36(T) - 0.18(M) + 6.55(TM)
T = 65.89 - 0.43(T) - 0.13(M) + 3.37(TM)
HDL = 65.89 - 0.43(T) - 0.13(M) + 3.37(TM)
HDL = -0.36(T) - 0.18(M) - answer ✅✅HDL = 39.24 - 0.36(T)
- 0.18(M) + 6.55(TM) A company wants to hire employees who are most likely to be successful at selling the company's products. The data analyst needs to determine if intelligence and friendliness predict sales performance of current employees. The current employees are given tests to measure both factors, and their sales performance data is checked, giving the company three scores for each employee. What is the criterion variable for this study? YOUR ANSWER CORRECT ANSWER Friendliness Intelligence Strategy results Sales performance - answer ✅✅Sales performance
Choose 2 answers Dependent variable is continuous. Independent variable is texting condition. The distribution is skewed. A t-test should be used. - answer ✅✅Independent variable is texting condition. A t-test should be used. A data analyst is performing logistic regression on elements with high multicollinearity. What is an assumption of logistic regression that is being violated? YOUR ANSWER CORRECT ANSWER Normally distributed variables Variable independence High R 2
Categorical data type - answer ✅✅Variable independence A data analyst is studying the relationship between gender and marriage using the result below: T = test: Paired two sample for means Married Gender Mean 0.48 0. Variance 0.26 0. Observations 25 25 Pearson correlation 0. Hypothesized mean difference 0 df 24 T stat -1. Confidence level 0. P (T<=t) one-tail 0. t critical one-tail 1. P (T<=t) two-tail 0. t critical two-tail 2. Given a confidence level of 95%, what can be concluded? There is no significant difference of mean between these two groups given the t-values.
53 - answer ✅✅ 36 A data analyst needs to determine whether antioxidants in blackberries can reduce age-related cognitive decline. Twenty-five adults between 65 and 80 are selected to eat blackberries for six months and be retested. The original scores are compared with the second scores to determine whether there was decline. What is the appropriate model to test the hypothesis? z test ANOVA Linear regression Two-sample t-test - answer ✅✅Two-sample t-test A data analyst studying dieting habits selects 24 athletes and divides them into groups by age (over 35, and 35 or under) and by whether they are dieting (dieting, or not dieting). Ten of the athletes are dieters, and 12 of the athletes are over 35.
The hypothesis is: Athletes in both age groups are equally likely to diet. Given the following tables: Data Table 35 and Under Over 35 Totals Dieting 1 9 10 Not Dieting 11 3 14 Column Totals 12 12 24 Expected 35andUnder Over35 Totals Dieting 0 10 10 Not Dieting 12 2 14 Column Totals 12 12 24 What can be concluded from the study? YOUR ANSWER CORRECT ANSWER Reject the null hypothesis Variables are not fixed Distribution is normal p-values are approximate - answer ✅✅Reject the null hypothesis
ANOVA
t-test Logistic regression Principal component analysis - answer ✅✅ANOVA t-test A junior data analyst intern is using linear regression to predict climate change. Given the following model: GAT ~ 0 + 0.2 OR + 0.1 GOT + 0.4 EAPG + 0.05 (EAPG) (OR) Given the following values:
- OR = 10
- GOT = 5
- EAPG = 4 What is the correct result?
6.1 - answer ✅✅6.
A researcher builds a multiple regression model. While testing the model, the researcher tests the model assumptions. Which assumption violates the standard model assumptions? YOUR ANSWER CORRECT ANSWER The variance of the model is constant. The model terms are additive. The error terms are dependent. The model parameters are constant. - answer ✅✅The error terms are dependent. A researcher is studying the effect of two medicines that treat insomnia. The medicine is tested on 40 people with insomnia. Given the results in the following table: Medication Cured Not Cured Medication 1 18 7
ANSWER CORRECT
ANSWER
Simulation study Fisher's exact test Two-sided hypothesis test Chi-square test - answer ✅✅Two-sided hypothesis test A researcher uses a chi-square test to find χ 2 = 6.78. Which conclusion can be drawn from this? YOUR ANSWER CORRECT ANSWER Due to the small value of χ 2, observed and expected counts are the same. The χ 2 value does not allow conclusions, and a p-value must be calculated. The χ 2 value is greater than 3.84, thus the null hypothesis should be rejected. Due to the small value of χ 2, observed and expected counts are different. - answer ✅✅The χ 2 value does not allow conclusions, and a p-value must be calculated.
A scientist is studying which factors will affect tree height. Data from 100 trees is collected. The independent variables are the trees' location, ambient temperature, and soil type. Given the following multiple linear regression model, which is being used to analyze the results: Tree height ~ 3.52 tree location + 5.23 ambient temperature + 2.15 soil type The scientist tests the model's validity using the F-test and calculates the R 2 value. The R 2 value for this model is 0.93, F 2, 97 is 8.02, and F 97, 2 is 99.3. Which conclusion can be made? YOUR ANSWER CORRECT ANSWER The p-value is equal to 0.07, indicating a bad fit for the model. F 2, 97 is less than F 97, 2, indicating a good fit for the model. R 2 is less than 1, indicating a bad fit for the model. R 2 is approaching 1, indicating a good fit for the model. - answer ✅✅R 2 is approaching 1, indicating a good fit for the model.
(0.13, 14.67) - answer ✅✅(0.13, 14.67) A study comparing graduating cumulative GPAs from students with two different majors is conducted to study the effect of each major on academic achievement. From the list of all graduating students in both majors, a random sample of 30 students from Major One and 30 students from Major Two are selected. The researcher decides to use an ANOVA test for this study. What will the researcher need to calculate? Sample size and sample mean Group means and standard deviations Population mean and standard deviation Percentage of the population sampled and population mean
- answer ✅✅Group means and standard deviations A study is done to determine if the color of an apple affects the purchase rate by consumers at a grocery store. Purchase counts for three colors of apples are collected.
Which technique should be used to determine if there is a difference in purchase rate by color? Rank-based Randomization t-test ANOVA - answer ✅✅ANOVA An analyst is tasked with testing a case with a proportion of success that is close to 0%. A chi-square test is used. What is the assumption for this method? YOUR ANSWER CORRECT ANSWER Contingency tables are limited to 2×2 sizing Expected count is calculated based on the distribution following the alternative hypothesis Separate samples for each proportion should be assumed Large sample to allow for expected values greater than 5 - answer ✅✅Large sample to allow for expected values greater than 5
The response variable denoted by y; will work as constant The confounding variable denoted by y; will determine the claim segment The coefficient value denoted by β; will be nonsignificant An explanatory variable that helps determine claim segment. - answer ✅✅An explanatory variable that helps determine claim segment. During the interaction assessment stage using the following dataset: Variable Abbreviation Coding Type of Hospital HT 1 = public, 0 = private Size of Hospital HS 1 = large, 0 = small Degree of contamination CT 1 = contaminated, 0 = clean Income INC Continuous Gender GN 1 = female, 0 = male Drinker DRK 1 = Yes, 0 = No Factors p-value HT x CT 0. HT x GN 0. HT x INC 0. HT x HS 0.
HT x DRK 0. CT 0. Using the hierarchy principle, which two variables should be retained for all further models considered? Choose 2 answers GN INC HS CT DRK - answer ✅✅GN CT Following the result of a PCA, the five principle components were decided as shown in the following table: PCA Variable 1 2 3 4 5 Climate 0.158 0.069 0.801 0.377 0. Housing 0.384 0.139 0.08 0.197 -0. Health 0.411 -0.372 -0.019 0.113 0. Crime 0.259 0.474 0.128 -0.042 0. Transportation 0.375 -0.141 -0.141 -0.43 0.
