STP Data Analysis 3 — Questions and Answers
Question 1: A researcher finds a p-value of 0.03. This means:
- There is a 3% chance the null hypothesis is true
- There is a 3% probability of obtaining these results if the null hypothesis is true (Correct answer)
- The effect size is clinically significant
- The study has 97% power
Correct answer: There is a 3% probability of obtaining these results if the null hypothesis is true
A p-value represents the probability of obtaining the observed results (or more extreme) assuming the null hypothesis is true.
Question 2: Which type of error occurs when a true null hypothesis is incorrectly rejected?
- Type II error
- Type I error (Correct answer)
- Systematic error
- Random error
Correct answer: Type I error
A Type I error (false positive) occurs when the null hypothesis is rejected despite being true, with probability equal to alpha.
Question 3: In receiver operating characteristic (ROC) analysis, an AUC of 0.5 indicates:
- A perfect diagnostic test
- A test no better than random chance (Correct answer)
- Moderate discriminatory ability
- High sensitivity with low specificity
Correct answer: A test no better than random chance
An AUC of 0.5 corresponds to the diagonal line, meaning the test performs no better than random chance at discrimination.
Question 4: What does a box-and-whisker plot's interquartile range (IQR) represent?
- The full range of all data points
- The middle 50% of the data (Correct answer)
- The standard deviation of the dataset
- The distance between the mean and median
Correct answer: The middle 50% of the data
The IQR spans from the 25th to the 75th percentile, encompassing the middle 50% of observations.
Question 5: When laboratory data shows positive skewness, the appropriate measure of central tendency is:
- Mean
- Mode
- Median (Correct answer)
- Geometric mean
Correct answer: Median
The median is preferred for skewed data as it is not influenced by extreme values that pull the mean in the direction of the skew.
Question 6: In a method validation study, 'trueness' refers to:
- The closeness of agreement between replicate measurements
- The closeness of agreement between the mean result and the true value (Correct answer)
- The ability to detect low concentrations of analyte
- The range over which results are proportional to concentration
Correct answer: The closeness of agreement between the mean result and the true value
Trueness describes systematic closeness of the measured mean to the accepted reference value, distinct from precision.
Question 7: Which of the following is an example of confounding in a research study?
- Random measurement error in the outcome variable
- A variable that is associated with both the exposure and the outcome (Correct answer)
- Missing data from participant dropout
- Incorrect calibration of laboratory instruments
Correct answer: A variable that is associated with both the exposure and the outcome
A confounder is a variable associated with both the exposure and outcome that can distort the observed relationship between them.
STP Data Analysis 3
A researcher finds a p-value of 0.03.
This means: