CLT Science Reasoning 2 — Questions and Answers
Question 1: A researcher wants to determine whether fertilizer type affects plant growth. She grows 30 plants, gives 10 plants Fertilizer A, 10 plants Fertilizer B, and 10 plants no fertilizer. All plants receive identical light and water. What is the control group?
- Plants given Fertilizer A
- Plants given Fertilizer B
- Plants given no fertilizer (Correct answer)
- All 30 plants combined
Correct answer: Plants given no fertilizer
The control group receives no treatment (no fertilizer), serving as the baseline for comparison.
Question 2: In an experiment testing reaction time, a scientist measures how quickly subjects press a button after a light flashes. The independent variable is:
- The reaction time recorded
- Whether the light is red or blue (Correct answer)
- The number of subjects tested
- The button used to respond
Correct answer: Whether the light is red or blue
The independent variable is what the experimenter manipulates — in this case, the color of the light.
Question 3: A study reports that students who eat breakfast score higher on tests than those who skip breakfast. Which conclusion is best supported?
- Eating breakfast causes higher test scores
- A correlation exists between breakfast and test performance (Correct answer)
- Skipping breakfast permanently damages cognition
- Test scores are unaffected by diet
Correct answer: A correlation exists between breakfast and test performance
Observational studies can establish correlation but cannot alone establish causation.
Question 4: Two scientists propose competing hypotheses about why a lake's fish population declined. Scientist 1 claims pollution caused the decline; Scientist 2 claims overfishing caused it. Which evidence would best distinguish between the two hypotheses?
- A survey of fish species diversity in the lake
- Water quality data combined with historical fishing records (Correct answer)
- The depth of the lake measured over 10 years
- Air temperature readings near the lake
Correct answer: Water quality data combined with historical fishing records
Comparing water quality data with fishing records directly tests both pollution and overfishing as potential causes.
Question 5: A table shows that as altitude increases, atmospheric pressure decreases. A student concludes that 'low pressure causes high altitude.' This reasoning is flawed because:
- The data contains measurement errors
- Correlation was mistaken for causation, and direction reversed (Correct answer)
- Not enough altitude levels were tested
- Atmospheric pressure is not measurable
Correct answer: Correlation was mistaken for causation, and direction reversed
Altitude drives pressure changes, not the reverse — the student inverted the causal direction and confused correlation with causation.
Question 6: An experiment is described as 'double-blind.' This means:
- Neither subjects nor researchers assessing outcomes know who received the treatment (Correct answer)
- Both eyes of each subject are tested independently
- Two separate research teams repeat the same experiment
- The data is analyzed without knowledge of the research question
Correct answer: Neither subjects nor researchers assessing outcomes know who received the treatment
Double-blind design prevents both participant and evaluator bias by keeping treatment assignments unknown to both parties.
Question 7: A scientist graphs enzyme activity (y-axis) versus temperature (x-axis) and observes activity rising from 0°C to 37°C then sharply falling to near zero by 60°C. The best explanation for the decline above 37°C is:
- The enzyme runs out of substrate
- Increased temperature provides too much energy for reactions to occur
- The enzyme denatures and loses its functional shape (Correct answer)
- Cold temperatures slow molecular movement
Correct answer: The enzyme denatures and loses its functional shape
High temperatures disrupt the enzyme's three-dimensional structure (denaturation), abolishing its catalytic function.
CLT Science Reasoning 2
A researcher wants to determine whether fertilizer type affects plant growth.
She grows 30 plants, gives 10 plants Fertilizer A, 10 plants Fertilizer B, and 10 plants no fertilizer.
All plants receive identical light and water.
What is the control group?