Statistics

Question 1

Why are statistics used in biology?

Answer 1

• Scientists typically collect data on a sample of a population to infer what is happening to the general population

Question 2

What is the first step in analysis?

Answer 2

• graph the data and examine the distribution

- yeah typical data will show normal distribution (bell shaped curve?)

Question 3

What does descriptive statistics allow?

Answer 3

• they allow for researchers to describe and quantify differences between data sets
• The distribution can be described by the mean, median, or mode, known as central tendencies

Question 4

What is a mean?

Answer 4

• The average of the data set

Question 5

What is a median? What happens if there are an even number of points?

Answer 5

• The middle number any range of data points

- if even number of points, average the two middle ones

Question 6

Why is the median useful in data sets that have measurements with extreme values or abnormal distribution?

Answer 6

• The median is not distorted by large or small measurements

Question 7

What is variability? (2)

Answer 7

• The measure of how far a data set diverges from the central tendency
• such as how spread out the data points are

Question 8

How is variability measured?

Answer 8

• measured by range and standard deviation

Question 9

What is the range? (2)

Answer 9

• The difference between the largest and smallest values

- A larger range indicate a greater spread of data

Question 10

What is the relationship between range and variability?

Answer 10

Larger range = greater variability
Smaller range = less variability
Often used in conjunction with standard deviation

Question 11

What is standard deviation?

Answer 11

• A measure of how spread out the data is from the mean

Question 12

What does low standard deviation mean? (2)

Answer 12

• means the data is closer to the mean

- the IV is likely causing changes

Question 13

What does high standard deviation mean? What does it mean in terms of the independent variable?

Answer 13

• The data is further from the mean (more spread out)

- factors other than the IV are likely causing changes

Question 14

What does the numbers of standard deviation represent?

Answer 14

1 Standard deviation from the mean in either direction on the horizontal axis represents 68% of the data
2 is 95%
3 is 99%

Question 15

What is the standard error of the mean?

Answer 15

• used to determine the precision and confidence in the mean value
  Such as how well does the mean of the sample represent the true mean of the population

Question 16

What is standard error of the mean based on?

Answer 16

Standard deviation (variability) and number of data points

Question 17

What are standard error bars?

Answer 17

They’re just added to the graphs and represent the standard error of the mean

Question 18

What does overlap of error bars mean?

Answer 18

• overlap means that the difference is not significant

- if they do not overlap, the difference may be significant

Question 19

What is mode? When is it useful?

Answer 19

• The value that appears most often in a data set

- Only useful when describing distribution of data for the mean and median would not be appropriate

Question 20

What happens if your standard deviation has a large spread? How about small? This is in terms of standard error of mean

Answer 20

A large spread means a large standard error of mean

A small spread has a low standard error of mean