AP BIO- Unit 0: Intro to Biology

guided test 9/12

Hypothesis

A question or theory that is being tested

Null Hypothesis

Trying to disprove, reject, or nullify a hypothesis

• “No effect”

• Ex: Adding nitrogen-rich fertilizer to the soil has no effect on the mean height of tomato plants; any difference in growth is due to random chance.

Alternative Hypothesis

Proving effect of independent variable on dependent variable

• Ex: Adding nitrogen-rich fertilizer to the soil significantly increases the mean height of tomato plants

Theory

A prediction made using backed up data

Scientific Law

Proven fact that can be used for all experiments

• tried repeatedly

Independent Variable

What’s being changed/ manipulated

• Ex. “Number of” “ Amount of”

Dependent Variable

What’s being measured

• Ex. “Score of” “Height of”

Inductive reasoning

Generalized conclusions based on observations and data

Deductive reasoning

Results derived from general conclusion

Control Group

Group that is not receiving treatment

Experimental group

Group that receives treatment

Constants

Variables that stay the same in the experiment

Variability

Things that can effect the validity of an experiment's outcome

• Ex. Time of day, Gender, Age

Mean

Average of all sums

• Ex. “n + n + n / 3”

Median

Middle datum in a group of data

Mode

Data that appears the most

• Ex: 555 66 77777 9 1 22 3 (ans: 7)

Range

Gap between highest and lowest data

• Ex: 51 and 79 (ans: 28)

Central Tendencies

A # that summarizes data set by finding middle position

Standard Deviation

How much data varies around the average “mean” score

Standard Error of the Mean (SEM)

How far data average is likely to be from population average

Quantitative data

Measured data

• Discrete

Qualitative data

Describes and can’t be measured

How to measure variability?

Standard deviation and range

Most reliable standard deviation

Low standard deviation. The data is close to the mean and is significant.

• IV is likely causing observed observations

If error bars overlap is the data significantly different?

No because it shows low variability/ high sample size (small errors)

When should a positive control be used?

When testing treatment

Variable meanings: X_i , x-bar, Summation symbol, n, n-1, s

1. X_i - Initial value/ data point

2. x-bar: Mean

3. Summation: Sum of values

4. n: sample size

5. n-1: Degrees of freedom

6. s: Standard deviation