Question

set 8.2

1. a drug company tested a new medication before putting it on the commercial market. pills without medication were given to 500 test subjects in group a, and pills with medication were given to 500 subjects in group b. in this experiment, the individuals in group a served as the (1) host group (3) control (2) dependent variable (4) hypothesis
2. in order to find the percentage of organic matter in soil from several different locations, a student collected the samples, weighed them immediately, roasted them for several minutes in a flame to burn off organic matter, and weighed them again. the student concluded that the difference between the first and second weights represented the weight of the organic matter in the soil. the most serious mistake that the student made in this experiment was in (1) taking large samples (2) weighing the samples before roasting them (3) failing to dry the samples before first weighing them (4) assuming that roasting could remove the organic matter
3. in an investigation to determine the effects of environmental ph on the germination of dandelion seeds, 25 dandelion seeds were added to each of five petri dishes. each dish contained a solution that differed from the others only in its ph, as shown below. all other environmental conditions were the same. the dishes were covered and observed for 10 days. the data table the student designed is shown below.

the effect of ph on seed germination
petri dish | ph of solution | number of seeds germinated
1 | 9 |
2 | 8 |
3 | 7 |
4 | 6 |
5 | 5 |
state the independent variable in this investigation. 1

Explanation:

Question 6

In an experiment, the control group is the one that does not receive the treatment being tested. Group A received non - medicated pills while group B received medicated pills. So group A is the control group.

Soil samples may contain moisture. Failing to dry the samples before weighing means the initial weight includes both soil and moisture. This will lead to inaccurate results for the weight of organic matter after roasting.

The independent variable is the variable that is deliberately changed or manipulated in an experiment. Here, the pH of the solution in each petri - dish is deliberately set to different values.

Answer:

(3) control

Question 7