Lab 2

Question 1

Scientific Method

Answer 1

step-wise process that allows scientists to formulate and test hypotheses relating to natural world

Question 2

Observation

Answer 2

observe study subject or phenomenon for a long period of time before considering conducting any experiments ,Observations lead to questions regarding behavior, habitat choices, food preferences, etc

Question 3

Abiotic vs. Biotic Variables

Answer 3

Abiotic Variables – nonliving components of environment that affect living creatures

Biotic Variables – living components of environment ex. Bacteria, other animals, fungi

Question 4

Question

Answer 4

form a question based on observations on subject/phenomenon

Ex: What environmental conditions do wood bugs prefer? What ecological functions do wood bugs perform?

Question 5

Hypothesis

Answer 5

testable explanation for observed phenomenon, provides reasonable explanation of phenomenon

Question 6

Null vs. Alternate Hypothesis

Answer 6

Null Hypothesis – statement that study subjects have NO preference for environmental conditions of the variable you are testing

Alternate Hypothesis – statement that suggests subjects DO have preference for one condition over another

Question 7

Do you indicate which of the two conditions the subjects might prefer?

Answer 7

No, Cannot be 100% sure of hypotheses

We can only take a sample of all specimen in the world

Therefore, while hypothesis can be rejected or modified, it cannot be proven with absolute certainty.

Usually a 5% error rate (p value = 0.05) is acceptable

Must be careful not to overstate conclusion

Question 8

Do we assume null hypothesis is correct? Do we prove hypotheses or disprove them?

Answer 8

Hypotheses are disproven, null hypothesis is assumed to be correct unless it is disproven, only then can we turn to the alternate hypothesis

Question 9

Experiment

Answer 9

experiments conducted to determine which hypotheses are supported

Question 10

Conclusion

Answer 10

draw conclusions once experiments are complete regarding phenomenon by rejecting or accepting null hypothesis

If hypotheses rejected, process starts over again

Question 11

What is stepbystep of scientific method?

Answer 11

OBSERVATIONS – QUESTION – HYPOTHESIS – PREDICTION (at least 3x repeats) - EXPERIMENTS OR NEW OBSERVATIONS – THEORY

Question 12

What are control tests?

Answer 12

tests that eliminate/reduces possibility that variables other than the one you are testing are causing the observed results, used as basis for comparing results to experimental tests

Question 13

What are experimental tests?

Answer 13

tests that only change one variable and making sure all other variables are constant

Question 14

Why is only one variable changed in experimental tests?

Answer 14

Make sure all other variables are constant and ONLY ONE is being affected, must be identical to be sure that they are responding only to the variable that is being changed

Otherwise, there will be an unanticipated factor in experimental design that is influencing their behavior, confusing results of experimental test

Question 15

Replication

Answer 15

doing experiment more than once

Question 16

Why do we replicate tests?

Answer 16

Doing an experiment once does not give experimenter much confidence, results of a single test may be due to chance

Demonstrates that results are reproducible and increases confidence in results

Decreases likelihood that observed results are due to chance

Increases likelihood that results observed are indeed response to conditions subjects were exposed to

Larger sample sizes produce more confidence in validity of results than smaller sample sizes

Question 17

what is the chi square test?

Answer 17

determines whether there is statistical significance to results

compares results of tests to what would be expected if subjects showed no preference to conditions of variable being tested

evaluates whether results observed differ significantly from those predicted by null hypothesis

Question 18

observed values

Answer 18

total results observed

Question 19

expected values

Answer 19

total results predicted by null hypothesis, always based on null hypothesis even in experimental tests

Question 20

Critical values

Answer 20

threshold value that depends on degrees of freedom and p-value

Question 21

p-value

Answer 21

probability that observed results are due to random fluctuations instead of variable being tested

threshold for determining whether results are different enough to reject null hypothesis

Question 22

If χ² is greater than or equal to critical value

Answer 22

reject null hypothesis and accept alternate hypothesis

Question 23

If χ² is less than critical value

Answer 23

fail to reject/ accept null hypothesis

Question 24

What is the equation of a chi-square test?

Answer 24

the sum of [(observed - exptected)^2 ] / expected

Question 25

How do you explain results of chi-square calcultion?

Answer 25

significance, compare chi-square value to critical value (less than, greater than, equal), rject/accept null hypothesis, yes/no preference

Question 26

Atleast how many replications should be performed?

Answer 26

3 replications to reduce likelihood of results being due to chance and to increase confidence in results

Question 27

Can a hypothesis ever be proven?

Answer 27

cannot be 100% sure because we can only take a sample of all the specimen in the world and therefore cannot be proven with absolute certainty

Question 28

What happens if a hypothesis is rejected?

Answer 28

it will be modified and revised and then experimented until results are consistent

Question 29

distinguish between an experimental and control test

Answer 29

experimental - one variable is changed
control - no changed variables, conditions kept as constant as possible

Question 30

what does it mean to have a p-value of 0.05?

Answer 30

There is a 5% chance that observed results were due to random fluctuations instead of variable being tested