Take this Quiz: GED and HiSET science — evidence and conclusions | Zestly

Question 1

A gardener wants to know if a new fertilizer helps tomato plants grow taller. She gives the fertilizer to ten plants and measures their height after four weeks. She does not give the fertilizer to any other plants. Why is this study design weak?

Accepted Answer

There is no control group to compare the growth against.

Answer

The sample size of ten plants is too small to measure height.

Answer

The gardener should have measured the width of the plants instead.

Answer

The study duration of four weeks is too short for any growth to occur.

Question 2

A researcher tests a new lightbulb by measuring its brightness in lumens. He records the following four readings: 800, 805, 795, and 800. What does the spread of these readings indicate?

Accepted Answer

The measurement process is consistent, as the values are very close.

Answer

The lightbulb is defective because the readings are not identical.

Answer

The average brightness is lower than the manufacturer claimed.

Answer

The lightbulb's brightness changes significantly over time.

Question 3

A survey finds that people who drink more coffee report lower stress. A news report announces that coffee reduces stress. The survey measured only how much coffee people drank and how stressed they felt, both on the same day. Which objection does that design most directly invite?

Accepted Answer

The arrow may point the other way: people who are already less stressed may be the ones with time to sit down with a coffee.

Answer

Coffee contains caffeine, which is a stimulant, so the finding is impossible.

Answer

The survey should have asked people which brand of coffee they drank.

Answer

Surveys can never tell us anything about human behavior.

Question 4

A factory manager tests whether increasing the conveyor belt speed affects the number of defective parts. She changes the belt speed and counts the defects. What are the independent and dependent variables?

Answer

Independent: belt speed; Dependent: number of defects.

Answer

Independent: number of defects; Dependent: belt speed.

Answer

Independent: factory temperature; Dependent: belt speed.

Answer

Independent: number of defects; Dependent: factory temperature.

Question 5

A doctor gives a new medicine to one patient, whose symptoms clear up within a week. She concludes that the medicine works. Why does a single case not support that conclusion?

Answer

Because a single patient might have been given the wrong dose.

Answer

Because one case gives nothing to compare against: the patient might have recovered anyway, in the time an untreated illness takes to pass.

Answer

Because medicines must be tested in a laboratory before they are given to any patient.

Answer

Because one week is too short a period for any medicine to act at all.

Question 6

A researcher wants to know whether room temperature affects typing speed. He tests one group of people in a room at 60 degrees and another in a room at 75 degrees. What must he hold constant between the two rooms?

Answer

The temperature, so that the two groups are treated the same way.

Answer

The color of the walls, since wall color is known to change how fast people type.

Answer

The typing task and the time allowed for it, so that any difference in speed can be laid to the temperature.

Answer

The exact age of every participant, since a study whose participants differ in age cannot be valid.