Unit 1: Statistical Analysis

Question 0

What factors determine the number of samples in an experiment?

Answer 0

Time, money, and people available to do the science

Question 1

What does observation result in?

Answer 1

The collection of measurable data

Question 2

What do samples represent in an experiment?

Answer 2

The entire population of the sampled thing

Question 3

What is statistics?

Answer 3

A branch of mathematics which allows us to sample small portions from habitats, communities, or biological populations, and draw conclusions about the larger population by mathematically measuring the differences and relationships between sets of data.

Question 4

What is the mean?

Answer 4

The average of the data points; the central tendency of the data

Question 5

What is the range?

Answer 5

Calculating the difference between the largest and smallest observed values

Question 6

What are outliers?

Answer 6

Unusually large or small data points that would have a great effect on the range

Question 7

What is standard deviation?

Answer 7

A measure of how the individual observations of a data set are dispersed or spread around the mean

Question 8

What is the abbreviation for standard deviation?

Answer 8

SD

Question 9

What are error bars?

Answer 9

A graphical representation of the variability of the data

Question 10

What can error bars be used to show?

Answer 10

Either the range of data or the standard deviation on a graph

Question 11

What do we use standard deviation to do?

Answer 11

To summarise the spread of values around the mean and to compare the means and spread of data between 2 or more samples

Question 12

What percent of all values lie within +/- 1 standard deviation of the mean in normal distribution?

Answer 12

68%

Question 13

What percent of all values lie within +/- 2 standard deviations from the mean in normal distribution?

Answer 13

95%

Question 14

What size is the standard deviation when the data points are clustered together?

Answer 14

Small

Question 15

What size is the standard deviation when the data points are spread apart?

Answer 15

Large

Question 16

What is the shape of a graph of normal distribution?

Answer 16

Bell curve

Question 17

If the bell curve is flatter, what size would the standard deviation be?

Answer 17

Large

Question 18

If the bell curve is taller and thinner, what size would the standard deviation be?

Answer 18

Small

Question 19

Why is standard deviation showing the spread of data around the mean useful?

Answer 19

It tells you how many extremes are in the data

Question 20

If there are many extremes in the data, what size will the standard deviation be?

Answer 20

Large

Question 21

If there are few extremes in the data, what size will the standard deviation be?

Answer 21

Small

Question 22

How is the standard deviation useful for comparing the means of two or more sets of data?

Answer 22

When comparing two sets of data which have exactly the same mean, we must also look at the standard deviation, because if the standard deviation of one data set is much higher than the other, it indicates a very wide spread of data around the mean for that data set; this makes us question the experimental design that is cause this wide variation in the data

Question 23

Why is it important to calculate the standard deviation in addition to the mean of a data set?

Answer 23

If we looked only at the mean, we would not see that one data set may be more variable than the other

Question 24

What is the t-test commonly used to determine?

Answer 24

Whether or not the difference between two sets of data is a significant (real) difference

Question 25

What is "p" in a t-test?

Answer 25

Probability that chance alone could produce the difference

Question 26

What is the probability that the difference is due to chance if p=0.05? Is it significant?

Answer 26

5%, yes

Question 27

What does it mean if p=0.5?

Answer 27

There is a 95% chance that the difference is due to the independent variable and not chance

Question 28

What percentage chance is significant in statistics?

Answer 28

95%

Question 29

Even though statisticians are never completely certain, they like to be at least what percent that their findings are significant and not due to chance before drawing conclusions?

Answer 29

95%

Question 30

What is used to calculate the value of "t"?

Answer 30

Mean, standard deviation, and sample size

Question 31

How do you find the degrees of freedom?

Answer 31

Find the sum of the sample sizes of each of the two groups, then subtract 2

Question 32

How do you find "p" when given a calculated value of "t" and a table of "t" values?

Answer 32

Find the degrees of freedom, then look in the left-hand column headed "degrees of freedom" and then across to the given t value; find the p value at the bottom of the column for the given t value

Question 33

What do experiments provide?

Answer 33

A test which shows cause (causation)

Question 34

What can observations without an experiment only show?

Answer 34

A correlation

Question 35

Correlation does not mean what?

Answer 35

Causation

Question 36

What story includes an interesting correlation example?

Answer 36

Africanized honey bees (AHBs) invading the USA

Question 37

When and where were Africanised honey bees discovered in the US?

Answer 37

In 1990, outside a small town in Texas

Question 38

How did AHBs come to the Americas?

Answer 38

They were brought from Africa to Brazil in the 1950s I. The hope of breeding a bee adapted to the South American tropical climate, but by 1990, they had spread to the southern US

Question 39

What did scientists predict would happen if AHBs came into the US?

Answer 39

They would invade all the southern states of the US, but this hasn't happened

Question 40

Where have the AHBs remained?

Answer 40

In the southwest states of the US

Question 41

What point coincides with get area around the areas where the AHBs have remained?

Answer 41

That there's an annual rainfall of 137.5 cm (55 inches) spread evenly throughout the year

Question 42

What seems to be a barrier to the movement of the AHBs and why?

Answer 42

The level of year-round wetness from even rainfall throughout the year, because the AHBs do not move into such areas

Question 43

What does the value of "r" signify when using a mathematical correlation test?

Answer 43

The correlation

Question 44

What does an r-value of +1 show?

Answer 44

A completely positive correlation

Question 45

What does an r-value of 0 show?

Answer 45

No correlation

Question 46

What does an r-value of -1 show?

Answer 46

A completely negative correlation

Question 47

What is required to find the cause of observed correlation?

Answer 47

Experimental evidence

Question 48

Even if there is a high correlation, only carefully designed experiments can do what?

Answer 48

Separate causation from correlation

Question 49

What does the null hypothesis state?

Answer 49

The difference observed is due to chance and therefore is not significant