Lab 2b

Question 1

what is a sample

Answer 1

A sample is a smaller group of members of a population selected at random to represent the population. Put another way, a sample is a subset of the population.

Question 2

The importance of sample size.

Answer 2

The bigger your sample size, the more likely your sample will be similar to the population you are sampling from.
Larger sample sizes provide more accurate mean values, identify outliers that could skew the data in a smaller sample and provide a smaller margin of error

Question 3

confidence interval?

Answer 3

by 1/√n . 95% confidence

Question 4

Biological replicates

Answer 4

parallel measurements of biologically distinct samples that capture random biological variation

Question 5

Technical replicates

Answer 5

repeated measurements of the same sample. The point of a technical replicate is to establish the variability (experimental error) of the analysis technique (the protocol and/or equipment you used and/or human error).

Question 6

you can have 2 different groups of subjects (test and control groups). In this case, the subjects are ____ to the groups

Answer 6

randomly assigned

Question 7

two types of statistics

Answer 7

Descriptive statistics

Inferential statistics

Question 8

Descriptive statistics ?

Answer 8

Descriptive statistics provide simple summaries about the sample and the dependent variable measured. For example, the average student grade in General Biology I at Dawson last year was 74%.

Question 9

Inferential statistics ?

Answer 9

Inferential statistics is used to make judgments of the probability that an observed difference between groups is due to the independent variable, or if it is one that might have happened by chance in this study.

Inferential statistics are used to determine how confident you are that the results (in this example grades on the standardized test) were caused by the independent variable (the CEGEP you went to), and not by chance (ex what if by chance, the students who went to Dawson had higher IQs than those who went to the other CEGEP and so scored higher because of their IQ, not because of the classes they took at Dawson?).

Question 10

Descriptive stats are used to ___ so we can get an overview of the results.

Answer 10

summarize data

Question 11

We can present the data in ____ and report the ___ as well as the ___observed.

Answer 11

tables and graphs

mean values

variability

Question 12

To be able to say how much the heart rate increased after exercise, you will need to use ___

Answer 12

descriptive statistics.

Question 13

To determine if the increase was significant, you would need to do ___

Answer 13

inferential statistics.

Question 14

What is the Range

Answer 14

The range is the difference between the smallest and the largest values of the data set—the wider the range the greater the variation.

Question 15

Variance ?

Answer 15

Variance measures how data values vary about the mean.

you first calculate the mean.
Second calculate the deviation of each sample from the mean
Third, square each deviation
Fourth; sum the squared deviations.
Lastly, divide the sum of squared deviations by the number of data points minus one to calculate the variance (S2).
S2 = ∑ (xi – mean)2 / n-1.

Question 16

The mean and measures of variability (variance and standard deviation) are examples of ___

Answer 16

descriptive statistics.

Question 17

What is the importance of Biological replicates in an experiment

Answer 17

Biological replicates help you to capture random biological variation; ex. humans don’t all respond identically to exercise in terms of increase in heart rate (some increase a little, some a lot).

Question 18

What is the importance of Technical replicates in an experiment

Answer 18

Technical replicates help identify variation in technique. They help you to evaluate the precision and reproducibility of an assay, to determine if the observed effect can be reliably measured.

Question 19

inferences ?

Answer 19

conclusions

Question 20

null (no effect) hypothesis (H0)

Answer 20

The H0 states that the difference in the dependent variable between the two treatment groups is not statistically significant. In other words, your independent variable has no effect on your dependent variable.

Question 21

alternative (effect) hypothesis (HA)

Answer 21

The HA states that the difference in the dependent variable between the two groups is statistically significant.

Question 22

two-tailed hypothesis?

Answer 22

A non-directional hypothesis . (ex. Young people will have a different blood pressure than older people.)

Question 23

one-tailed hypothesis?

Answer 23

directional hypothesis (ex. Young people will have a higher blood pressure than older people)

Question 24

The _______the calculated p-value, the higher the significance.

Answer 24

smaller

Question 25

The t-test is used to determine whether the difference between the means of two groups is ___significant.

Answer 25

statistically

Question 26

The ___the difference and the ___the variability of the data within each group, the more likely that the difference is statistically significant.

Answer 26

LARGER

SMALLER

Question 27

Unpaired t-test

Answer 27

compares two independent groups ex. diabetic patients versus non-diabetics.

Question 28

paired t-test

Answer 28

comparing and testing 2 sets of data that are somehow related, based on 2 samples. Usually this happens when measurements are taken “Before and After” a certain treatment or event; essentially, you test the same samples under two different conditions. So, the samples are not ‘independent’ samples.

Question 29

Which t-test (unpaired or paired) would you use to compare A. the heart rate of Dawson students

Answer 29

paired

Question 30

. Describe a protocol to test the following hypothesis: Hypothesis: the ability to recall words is reduced when studying with music on, as compared to when studying in silence. A) First describe a protocol that would be unpaired and then B) re-write the protocol for a paired t-test.

Answer 30

A) Unpaired t-test:

100 STUDENTS STUDY WITH MUSIC TEST SCORE
100 DIFFERENT STUDENTS STUDY WITHOUT MUSIC TEST SCORE

B) Paired t-test:

100 STUDENTS STUDY WITH MUSIC TEST SCORE,
THE SAME 100 STUDENTS STUDY WITHOUT MUSIC TEST SCORE

BETTER:
50 STUDENTS STUDY WITH MUSIC TEST SCORE, SAME TIME 50 STUDENTS STUDY WITHOUT MUSIC TEST SCORE
THEN U SWAP

Question 31

If the p-value is ≥ 0.05, then you fail to _____: The difference __ statistically significant.

Answer 31

reject your null hypothesis (the H0)

IS NOT

Question 32

If the p-value is < 0.05, then you accept __ie you reject the H0 and conclude that the difference__ statistically significant.

Answer 32

your alternative hypothesis (the HA)

IS

Question 33

what is allelopathy?

Answer 33

allelopathy refers to the phenomenon where a plant either hinders or stimulates the growth of surrounding plants. the plants produce and release allelochemicals which are substances that influence the growth, germination, and reproduction of other organisms.

Question 34

advantages of allelopathy for a plant?

Answer 34

by preventing the growth of other plants, the allelopathic plant can protect their space by the release of allelochemicals which allow its roots to draw more nutrients from the soil, stimulating their growth.

Question 35

sample vs population

Answer 35

A population is the entire group that you want to draw conclusions about. A sample is the specific group that you will collect data from.

Question 36

importance of a statistical test.

Answer 36

Tests for statistical significance are used to estimate the probability that a relationship observed in the data occurred only by chance

Question 37

what is the purpose of a t test

Answer 37

A t-test is a type of inferential statistic used to determine if there is a significant difference between the means of two groups, which may be related in certain features.

Question 38

what does the t test compare

Answer 38

A t-test is a statistical test that is used to compare the means of two groups, but it also includes the variability of the samples (see the denominator of the t-test equation).

Question 39

A statistically significant difference means that ?

Answer 39

A statistically significant difference means that the difference is unlikely to be due to chance and so it leads us to believe that the difference in the dependent variable is due to our manipulation of the independent variable. In other words, the independent variable had an effect on the dependent variable.