Statistics CERTIFIED-DATA-SCIENCE-PRACTITIONER Practice Questions (Page 4)

Questions 16–20

1. 16application · medium

   A study with 10,000 participants finds a statistically significant correlation (p < 0.001) between hours of sleep and job performance, with r = 0.12. The HR director wants to implement a mandatory sleep program based on this finding. What is the most important consideration before acting?

   • AThe correlation coefficient of 0.12 indicates a weak effect, so the practical impact of the program may be minimal despite statistical significance.
   • BThe sample size is too large, so the p-value is invalid and the result should be ignored.
   • CThe p-value is extremely small, so the relationship is definitely strong enough to justify the program.
   • DThe correlation proves that sleep causes improved job performance, so the program will work.
   Reveal Solution Discussion Select an answer first
2. 17foundation · medium

   How does increasing the sample size affect the width of a confidence interval, assuming all else remains constant?

   • AIt narrows the interval
   • BIt widens the interval
   • CIt changes the confidence level
   • DIt has no effect on the interval width
   Reveal Solution Discussion Select an answer first
4. 18application · medium

   A data scientist at a retail company runs an A/B test comparing a new checkout flow (Group B) against the current flow (Group A). With 50,000 users per group, the conversion rate is 3.2% for Group A and 3.5% for Group B. A two-proportion z-test yields a p-value of 0.04. The product manager wants to roll out the new flow. What should the data scientist do before recommending the rollout?

   • AReport the p-value and recommend rollout because 0.04 is below the 0.05 significance level.
   • BCompute Cohen's h or the absolute conversion lift to assess whether the 0.3 percentage-point difference is practically meaningful.
   • CRe-run the test with a larger sample because a p-value of 0.04 is too close to 0.05 to be trustworthy.
   • DSwitch to a chi-square test because the z-test is invalid for proportions.
   Reveal Solution Discussion Select an answer first
5. 19foundation · medium

   In a statistical hypothesis test, what does the p-value represent?

   • AThe probability that the null hypothesis is true
   • BThe probability that the alternative hypothesis is true
   • CThe probability of making a Type II error
   • DThe probability of observing the test statistic or something more extreme, assuming the null hypothesis is true
   Reveal Solution Discussion Select an answer first
6. 20expert · medium

   A data scientist computes a 95% confidence interval for the mean difference in sales between two marketing campaigns as [-$500, $1,500]. The marketing director wants to know if Campaign B is better than Campaign A. What is the most accurate conclusion?

   • AThe difference is not statistically significant at the 0.05 level because the interval contains 0.
   • BCampaign B is significantly better because the interval includes positive values.
   • CThe result is inconclusive because the interval is too wide to make any decision.
   • DCampaign A is significantly better because the interval includes negative values.
   Reveal Solution Discussion Select an answer first