ISAT Interpreting Scientific Data 3 — Questions and Answers
Question 1: A data table shows average rainfall (mm) and crop yield (tons/hectare) for 8 regions. As rainfall increases, crop yield increases up to 800 mm, then decreases. What type of relationship is this?
- Linear positive correlation
- Linear negative correlation
- Non-linear (curvilinear) relationship (Correct answer)
- No relationship
Correct answer: Non-linear (curvilinear) relationship
A relationship that increases then decreases forms a curve (inverted U-shape), which is a non-linear or curvilinear pattern.
Question 2: A scientist graphs reaction rate (y-axis) versus enzyme concentration (x-axis). The graph levels off at a maximum rate. What most likely explains the plateau?
- The enzyme becomes denatured at high concentrations
- The substrate concentration has become the limiting factor (Correct answer)
- Temperature was not controlled
- The experiment ran out of time
Correct answer: The substrate concentration has become the limiting factor
When enzyme concentration exceeds available substrate, reaction rate plateaus because substrate is now the limiting factor.
Question 3: Two overlapping histograms compare the distribution of exam scores for morning vs. afternoon test-takers. Both distributions are roughly symmetric. The morning peak is at 75 and the afternoon peak is at 68. What can be concluded?
- Morning test-takers are inherently smarter
- Morning test-takers scored higher on average in this dataset (Correct answer)
- The afternoon exam was harder
- Time of day has no effect on performance
Correct answer: Morning test-takers scored higher on average in this dataset
The data shows a difference in central tendency (peak scores), but cannot establish causation or compare exam difficulty without additional information.
Question 4: A researcher finds a strong negative correlation (r = −0.89) between hours of sleep and number of errors on a cognitive task. What does this correlation value indicate?
- More sleep causes fewer errors
- As sleep hours increase, errors tend to decrease strongly (Correct answer)
- Sleep and errors are unrelated
- The relationship is weak and positive
Correct answer: As sleep hours increase, errors tend to decrease strongly
r = −0.89 indicates a strong negative correlation: as one variable increases, the other tends to decrease, though correlation does not imply causation.
Question 5: A toxicology study reports the LD50 of a substance as 200 mg/kg. What does this value represent?
- The dose that cures 50% of test animals
- The dose lethal to 50% of a test population (Correct answer)
- The maximum safe dose for all organisms
- The dose that causes symptoms in 50% of cases
Correct answer: The dose lethal to 50% of a test population
LD50 (lethal dose 50) is the dose required to kill half of a tested population, used as a standard measure of acute toxicity.
Question 6: A study measures body temperature every hour for 24 hours. The data shows values between 36.1°C and 37.2°C with no clear trend. Which statistical measure best summarizes the typical body temperature?
- Range
- Standard deviation
- Mean (Correct answer)
- Variance
Correct answer: Mean
The mean provides a single representative value for the central tendency of normally distributed data like body temperature.
Question 7: A graph shows two lines: one for observed sea level rise and one for projected rise based on a climate model. The lines diverge after 2050. What does the divergence most likely represent?
- Measurement error in past observations
- Increasing uncertainty in long-term projections (Correct answer)
- A proven decrease in sea level rise rate
- The end of the observational period
Correct answer: Increasing uncertainty in long-term projections
Diverging projection lines typically represent widening confidence intervals, reflecting increasing uncertainty as projections extend further into the future.
ISAT Interpreting Scientific Data 3
A data table shows average rainfall (mm) and crop yield (tons/hectare) for 8 regions.
As rainfall increases, crop yield increases up to 800 mm, then decreases.
What type of relationship is this?