Standard Deviation

Question 1

what is correlation?

Answer 1

when a change in one variable is reflected by a change in the other variable, you cannot conclude that the change in one caused the other

Question 2

what is a casual relationship?

Answer 2

when a variable causes a change in another variable

Question 3

what is standard deviation?

Answer 3

the spread of data from the mean

Question 4

why is standard deviation better than the range?

Answer 4

the range only takes into account the highest and lowest values in the data set , range is more influenced by a single outlier than SD

Question 5

what does a large SD in relation to the mean suggest?

Answer 5

the data is highly variable, less reliable data

Question 6

what does a small SD in relation to the mean suggest?

Answer 6

there is little variation in the data, the values are all very similar, more reliable data

Question 7

why are 2 SD’s better than 1?

Answer 7

2 SD from the mean incorporate 95% of all the data

Question 8

what does it mean if SD’s overlap?

Answer 8

there is not a significant difference between the two sets of data

Question 9

what does it mean if the SD’s don’t overlap?

Answer 9

there is likely a significant difference between the two sets of data

Question 10

what are some things you must do during a biological investigation to make the data as reliable as possible?

Answer 10

• must have a control group
• must have all variables that would affect dependant variable controlled
• must do many repeats, making the mean more reliable
• assign groups randomly to avoid bias
• if investigating someone with a serious illness you must allow them to continue regular treatment for ethical reasoning
• use SD’s