BIO60 Lab Exam 1: Intro to Scientific Method

In the following hypotheses, which is the null hypothesis and which are the 2 alternative hypotheses? 1) Hand soap does not affect bacterial diversity. 2) Hand soap increases bacterial diversity. 3) Hand soap decreases bacterial diversity. *Note: these same hypotheses are used for Hand sanitizer, this example is just for hand soap

1) Hand soap does not affect bacterial diversity (Null hypothesis). 2) Hand soap increases bacterial diversity (Alternative hypothesis 1). 3) Hand soap decreases bacterial diversity (Alternative hypothesis 2).

A t-test produces a test statistic called a p-value. What does the p-value tell you?

The P-value tells you whether the results are statistically significant, and whether the null hypothesis and alternative hypothesis are accepted or not.

What was the Dependent variable in the bacterial diversity lab?

The amount of Bacterial diversity

What was the control group in the bacterial diversity lab?

The control group was the group of unwashed hands. This allowed us to measure the bacterial diversity of unwashed hands.

What was the Independent variable/s in the bacterial diversity lab?

The use of either Hand Soap or Hand Sanitizer

Independent variable (hint: manipulated)

The variable that is manipulated/changed in an experiment

There can only be one null ______.

There can only be one null HYPOTHESIS.

T/F: A null hypothesis states that there is no relationship between the independent and dependent variables

True

T/F: There can be multiple alternative hypotheses.

True

True or False: Alternative hypotheses infer an effect between two variables.

True

Statistically, how did we determine which is more effective at decreasing bacterial diversity, hand soap or hand sanitizer?

We ran a t-test comparing the change in microbial diversity (between before hand soap/sanitizer and after hand soap/sanitizer, these were laid out in table of values) and found that p = 0.40, so the null hypothesis that "the reduction in bacterial diversity for hand soap is the same as that for hand sanitizer" was accepted.

(P value example) If p = 0.40 and the null hypothesis was "Hand soap and hand sanitizer equally decrease bacteria diversity," would we reject or accept the null hypothesis?

We would accept this null hypothesis because p > 0.05.

(P value example) If P < 0.001 in the bacterial diversity study and the related null hypothesis is "Hand sanitizer does not affect bacterial diversity," should we reject or accept the null hypothesis?

We would reject this null hypothesis, favoring an alternative hypothesis bc P < 0.05 here.

(P value example) If P < 0.001 in the bacterial diversity study and the related null hypothesis is "Soap does not affect bacterial diversity," should we reject or accept the null hypothesis?

We would reject this null hypothesis, favoring an alternative hypothesis bc P < 0.05 here.

The main Scientific Question of the antibacterial diversity lab

Which is more effective at decreasing bacterial diversity: hand soap or hand sanitizer?

Questions: (1) Does hand soap reduce bacterial diversity? (2) Does hand sanitizer reduce bacterial diversity? What are the hypotheses that match each of these questions?

(1) Hand soap reduces, does not affect, or increases bacterial diversity. (2) Hand sanitizer reduces, does not affect, or increases bacterial diversity.

Data analysis from an experiment yielded a p-value of 0.3. Consequently, the scientists ______ the null hypothesis and ________an alternative hypothesis.

Data analysis from an experiment yielded a p-value of 0.3. Consequently, the scientists ACCEPTED the null hypothesis and REJECTED an alternative hypothesis.

Example of a Good scientific question

Does a particular gene influence aging in mice? This is good bc it's specific, testable, and measurable.

Experiments must be _____ so it can be verified.

Experiments must be REPEATABLE so it can be verified.

Example of a hypothesis

Hand soap decreases bacterial diversity.

Example of a Bad scientific Question

How did life begin on earth? This is bad bc it is not specific enough and can't be tested.

Example of a prediction (Hint: If... then)

If hand soap is used (in the experiment), then bacterial diversity will decrease.

If the P-value is greater than or equal to 0.05, the null hypothesis is _______ and an alternative hypothesis is _______.

If the P-value is greater than or equal to 0.05, the null hypothesis is ACCEPTED and an alternative hypothesis is REJECTED.

If the P-value is less than 0.05, the null hypothesis is _______ and an alternative hypothesis is ________.

If the P-value is less than 0.05, the null hypothesis is REJECTED and an alternative hypothesis is ACCEPTED.

Question: Which is more effective at decreasing bacterial diversity: hand soap or hand sanitizer? What is a good hypothesis to match this question?

If there is a reduction in bacterial diversity, the reduction in bacterial diversity for hand soap will be greater, the same as, or less than sanitizer.

(Repeated bacterial diversity experiment) For the research question, "Is the reduction of bacterial diversity due to the chemicals in the soap and sanitizer treatments or to the action of rubbing the hands together?" Of the three hypotheses related to this question below, which is the null hypothesis and which 2 are the alternative hypotheses? 1) Rubbing hands together with water has no effect on bacterial diversity. 2) Rubbing hands together with water reduces bacterial diversity. 3) Rubbing hands together with water increases bacterial diversity.

1) Rubbing hands together with water has no effect on bacterial diversity. (Null hypothesis) 2) Rubbing hands together with water reduces bacterial diversity. (Alt hypothesis 1) 3) Rubbing hands together with water increases bacterial diversity. (Alt hypothesis 2)

For the final research question, "Which is more effective at decreasing bacterial diversity: hand soap or hand sanitizer?", Of the three hypotheses related to this question below, which is the null hypothesis and which 2 are the alternative hypotheses? 1) The reduction in bacterial diversity for hand soap is the same as that for hand sanitizer. 2) The reduction in bacterial diversity for hand soap is greater than that for hand sanitizer. 3) The reduction in bacterial diversity for hand soap is less than that for hand sanitizer.

1) The reduction in bacterial diversity for hand soap is the same as that for hand sanitizer (null hypothesis). 2) The reduction in bacterial diversity for hand soap is greater than that for hand sanitizer (alternative hypothesis 1). 3) The reduction in bacterial diversity for hand soap is less than that for hand sanitizer (alternative hypothesis 2).

Before testing the Scientific Question, "which is more effective at decreasing bacterial diversity: hand soap or hand sanitizer?," what 2 questions had to be answered to confirm that soap and sanitizer really reduce bacterial diversity?

1. Does hand soap reduce bacterial diversity? 2. Does hand sanitizer reduce bacterial diversity?

Steps of the Scientific Method

1. Observation 2. Question 3. Hypothesis 4. Prediction 5. Experiment 6. Analysis 7. Conclusion

What were the Experimental groups in the bacterial diversity lab, and what treatments did they receive?

2 experimental groups with 2 diff treatments: 1. Hand Soap 2. Hand Sanitizer

Dependent variable (hint: is measured)

A factor/outcome in an experiment whose value is measured to see if it is influenced by the manipulation in the independent variable. Depends on the independent variable

What are the characteristics of a good hypothesis?

A good hypothesis is: 1. Testable (thru experimentation & data analysis) 2. Falsifiable 3. Repeatable (Leads to repeatable experiments)

What are the components of a good scientific question?

A good scientific question is: 1. Testable (thru experimentation) 2. Will lead to measurable data 3. Specific

(Difference between a hypothesis & a prediction) A prediction is an "If.... then" statement specific to an ________, and a hypothesis is a possible explanation of an __________.

A prediction is an "If.... then" statement specific to an EXPERIMENT, and a hypothesis is a possible explanation of an OBSERVATION.

Example of an added control group (a shortcoming in the conclusion of the bacterial diversity experiment was that it didn't have a control group, so what specific control group did they add?)

After the initial experiment, we reran the experiment and added a control group in which the participants rubbed their hands together with water only.

Control group (hint: doesn't get the treatment

In an experiment, the group that does not receive the treatment, while all other variables are kept constant Used to establish a baseline for comparison

Experimental group (hint: receives the treatment)

In an experiment, the group that receives the treatment while all other variables are kept constant

After completing all bacterial diversity experiments we found that?

Rubbing hands with water is more effective at reducing bacterial diversity than leaving hands unwashed. Although the data showed using hand soap or hand sanitizer is more effective than just rubbing hands with water alone, neither hand soap nor hand sanitizer was shown to be superior at reducing bacterial diversity on hands.