Statistics

Question 1

What does a thin curve on a graph mean in standard deviations

Answer 1

Most values remain close to the average , and the standard deviation is small .

Question 2

What does a fat curve mean in standard deviation on a graph

Answer 2

Wider spread of values about the mean and the standard deviation is large

Question 3

What is standard deviation

Answer 3

The measure of how spread out your repeats are from your mean

Question 4

What is the advantage of using the standard deviation instead of the range?

Answer 4

1) SD shows the spread of data around the mean , whereas the range is only the difference between the highest and the lowest value .
2) SD reduces the effect of anomalies , whereas the range includes anomalies.
3) SD can be used to indicate whether a difference between results is significant .

Question 5

What happens if , when you add or minus your standard deviation from the means , there is no overlap

Answer 5

This indicates it is likely to be a significant difference

Question 6

What happens if , when you add or minus the standard deviation from the means, there is an overlap

Answer 6

This indicates there is likely to not be a significant difference between those means .

Question 7

How do you know if you are measuring Spearman’s Rank (correlation coefficient)

Answer 7

• If you collect continuous data , taking measurements
• If you are investigating an association between two measurements

Question 8

How do you know if you are measuring the Student T test

Answer 8

• If you’re collecting continuous data , taking measurements
• If you’re investigating a difference between two means

Question 9

How do you know if you’re calculating Chi-squared

Answer 9

• If you collect frequency data , counting how many individuals are in a category.
• If you’re investigating a difference

Question 10

What is Spearman’s rank (correlation coefficient)

Answer 10

Two continuous variables where you are investigating an association between these two measurements

Question 11

What is the null hypothesis of spearman’s rank ( correlation coefficient )

Answer 11

There will be no significant correlation between…. and ……
(Always assume there is no relationship )

Question 12

What value will Spearman’s rank always be

Answer 12

A number between -1 and +1

Question 13

What does a value of almost +1 mean in spearman’s rank

Answer 13

It’s a perfect positive correlation

Question 14

What does a value close to -1 mean in spearman’s rank

Answer 14

Perfect negative correlation

Question 15

What does the value of 0 mean in spearman’s rank

Answer 15

No correlation

Question 16

How do you figure out if the spearman’s rank value is significant or not

Answer 16

Compare it with a critical values table

Question 17

What is a P value in the critical values table in the correlation coefficient

Answer 17

P value is the probability that the correlation is due to chance

Question 18

How do you get a significant correlation using the critical values table in correlation coefficient

Answer 18

You must have less than a 5% (0.05) probability that the correlation is due to chance

Question 19

What is the conclusion if the value for the spearman’s rank does not exceed the p value ( the critical value )

Answer 19

There is more than a 5% probability that the correlation we have is due to chance
Therefore we accept the null hypothesis, so ……did not always result in ……

Question 20

EQ : A student investigated whether the concentration of glucose bacteria are grown in had an effect on the bacterial population size. The student did a statistic on the data and their calculated value equaled the critical value at P=0.5 . They concluded that the more glucose you add , the more bacteria there will be . Do you agree with this conclusion ? (3)

Answer 20

1) The graph does show a positive correlation between concentration of glucose and the number of bacteria
2) However the results overlap. For the same concentration of glucose there are multiple different results for the number of bacteria . This shoe a range in effect .
3) The correlation coefficient showed there was 50% (0.5) probability that the correlation was due to chance and therefore this is not a significant correlation , it must be less than 5% probability.

Question 21

How do we know if it is a paired T test

Answer 21

If the two sets of data are:
- from the same individual
- the results are paired
- both groups have the same sample size

Question 22

What does the conclusion for the t test include

Answer 22

• accept or reject null hypothesis
• is there more / less than 5% probability that the difference is due to chance

Question 23

What is the conclusion for the t test if it exceeds the p value of 0.05

Answer 23

Reject null hypothesis as the calculated value is more than the critical value
There is less than 5% probability that the difference is due to chance

Question 24

What is the conclusion for a T test if the calculated value doesn’t exceed the critical value of p= 0.05

Answer 24

Accept the null hypothesis , as the calculated value is less than the critical value .
There is more than 5% probability they the difference is due to chance

Question 25

What would be the hypothesis in chi squared

Answer 25

There will be no significant difference between the observed number of ….. and the expected number of ….

Question 26

What is chi squared

Answer 26

Looks at the difference in frequencies between categoric groups

Question 27

What is the conclusion when the calculated value of chi square exceeds the critical value of p= 0.05

Answer 27

Less than 5% probability that the difference between the observed and the expected value is due to chance.
This means the the null hypothesis can be rejected and there is a significant difference between …..

Question 28

What is the conclusion if the calculated value of chi square doesn’t exceed the critical value of p = 0.05

Answer 28

There is more than a 5% probability they the difference between the observed and the expected value is due to chance.
This means the null hypothesis can be accepted and there is no significant difference between ….