4. susan observed that different kinds and amounts of fossils were present in a cliff behind her house. she wondered why changes in fossil content occurred from the top to the bottom of the bank. she marked the bank at five positions: 5, 10, 15, 20 and 25 m from the surface. she removed 1 bucket of soil from each of the positions and determined the kind and number of fossils in each sample.

hypothesis:
independent variable:
dependent variable:
constant (at least one):
control:
number of groups:
number of trials per group:

A scientific experiment is divided into two sample groups: control and the experimental. The control group lacks the key variable to be studied while the experimental group contains the sample to be studied.

The experiment contains three experiments: the variable to be studied (dependent variable), the variable which can be changed and influence the dependent variable (independent variable) and the variable which do not change in the experiment (constant variable).

In the given experiment,  

1. Hypothesis: when the height changes in soil, the content of the fossil in the soil also changes.

2. Independent Variable: the height of the bank from surface

3. Dependent Variable: the number and type of fossil.

4. Constant variable: the amount of soil in the bucket

5. Control: the soil at the surface (0 cm)

6. Number of groups: 5 groups

7. Number of trials per group: should be 3

305.7

explanation:

density =m/v

density =917/3.00

density = 305.

approximately = 305.7

in four significant figures