Vaux Lectures 1, 2

Question 1

What formula is used to calculate SD?

Answer 1

SD=√((∑(X-M)^2)/(n-1))

Question 2

What formula is used to calculate SEM?

Answer 2

SEM=SD/(√N)

Question 3

What would be considered a descriptive statistic?

a. Standard error of the mean
b. Standard deviation
c. Confidence interval 
d. Poisson median

Answer 3

b. Standard deviation

Question 4

What happens as sample size increases?

a. The mean gets further away from the true mean
b. The range decreases
c. The standard deviation stays much the same
d. The standard error increases

Answer 4

c. The standard deviation stays much the same

Question 5

What must a figure legend contain?

a. The value of N
b. A description of the error bar used
c. A calculated P value greater than 0.05
d. A and B

Answer 5

d. A and B

Question 6

What might indicate that an image has been manipulated?

a. The background is clearly visible
b. Edges are blurry 
c. The axes of a graph begin at zero
d. Western blot bands have inconsistent “smiles”

Answer 6

d. Western blot bands have inconsistent “smiles”

Question 7

Which statement about standard deviation is incorrect?

a. Many biochemical journals require that data be graphed as mean +/- SD
b. When N is small, the sample SD often underestimates the SD of the population
c. It can be calculated using the average of the squared differences between each sample and the sample mean
d. It is a robust statistic and mean +/- SD encompasses approximately two thirds of data points in a normal distribution

Answer 7

a. Many biochemical journals require that data be graphed as mean +/- SD

Question 8

Consider the following experiment: you have triplicate cell cultures and repeat the experiment on four different occasions. What would be the value of N?

a. 4
b. SD x 3
c. 3
d. 12

Answer 8

a. 4

Question 9

A binomial distribution:

a. Is also referred to as a Poisson distribution
b. Does not consider variability or sampling error
c. Adopts a bell shape when p is close to 0.5 and N increases
d. Is used for continuous variables only

Answer 9

c. Adopts a bell shape when p is close to 0.5 and N increases

d wrong because it is used for discrete variables

Question 10

What is FALSE about a Poisson distribution?

a. It is seen when measuring discrete variables
b. It involves integer’s that are commonly less than zero
c. When plotted, the tail is longest towards the right
d. The expected SD is the square root of the mean

Answer 10

b. It involves integer’s that are commonly less than zero

Question 11

Which distribution would be used for a continuous variable such as weight or height?

a. Poisson
b. Normal
c. Binomial 
d. Inferential

Answer 11

b. Normal

Question 12

If a 95% Confidence Interval was generated 100 times by taking groups of samples from a population, how often would you expect to encompass the population mean?

a. 5 times
b. 100 times
c. 1 time
d. 95 times

Answer 12

d. 95 times

Question 13

A P value…

a. Is the probability of obtaining the difference you observed if you were actually sampling from a single population
b. Is the probability of getting the observed result if the null hypothesis were false
c. Is the probability that the gene or drug your testing does have a real effect
d. Is enough to conclude that a result is significant biologically as well as statistically when p < 0.05

Answer 13

a. Is the probability of obtaining the difference you observed if you were actually sampling from a single population

Question 14

When are statistics useful in cell biology?

a. When presenting and interpreting data for publication
b. When monitoring the conduct of experiments
c. When deciding which experiments are worth repeating
d. All of the above

Answer 14

d. All of the above

Question 15

What should NOT be included when preparing a western blot figure for publication?

a. Molecular weights
b. Loading controls
c. Cropped images of the bands with the background removed
d. A note stating that an image has been cut and joined (if applicable)

Answer 15

c. Cropped images of the bands with the background removed

Question 16

Which statement is false?

a. A conclusion can only apply to the population where you took the sample from
b. Replicates are useless in biological research because they do not add to the N value
c. Experimental design is the art of varying one factor at a time while controlling others
d. A N value of 1 holds little value in statistical relevance

Answer 16

b. Replicates are useless in biological research because they do not add to the N value

Question 17

When error bars between two conditions overlap, the difference between those conditions is not significant.

Answer 17

True

Question 18

When p < 0.05, it can be concluded that results are significant.

Answer 18

False

Consider effect size, biological importance, underlying mechanisms

Question 19

Descriptive error bars describe how the data is distributed whilst inferential error bars indicate the confidence in the mean.

Answer 19

True

Question 20

A value of P > 0.05 means that no effect exists.

Answer 20

False

Effect may be small, may need to repeat experiment more

Question 21

The shorter the length of an inferential error bar, the more “uncertain” the data.

Answer 21

False

Question 22

If N ≥ 10, the 95% confidence interval is approximately M +/- 2 x SE.

Answer 22

True

Question 23

When N = 1, it is critical to show error bars and the P value.

Answer 23

False

Question 24

It is not appropriate to show error bars and statistics for replicates.

Answer 24

True

Question 25

The SE becomes smaller as you repeat your experiment more and more because the SE varies inversely with the square root of N.

Answer 25

True

Question 26

If a figure shows SE bars, you could mentally half the width of them to get approximate 95% CIs.

Answer 26

False

You could DOUBLE them to achieve this. And N needs to be greater than 10.

Question 27

CI’s mean the same thing regardless of N.

Answer 27

True

Question 28

The range and SD are the most commonly used types of inferential statistics.

Answer 28

False

they are descriptive

Question 29

A high level of variability would lead to a wide range.

Answer 29

True

Question 30

In Poisson distributions, the expected SD is the square root of the mean.

Answer 30

True

Question 31

To ensure that a published figure is true and non-manipulated, it is best to print it out and view it on high quality paper.

Answer 31

False

Question 32

As N increases, SEM also increases.

Answer 32

False

Question 33

Representative results can be shown for numerical and nonnumerical data.

Answer 33

False

Only nonnumerical such as western blot

Question 34

If you’re the author of a paper, you don’t need to read it yourself if you know the first author is thorough and diligent.

Answer 34

False

Question 35

Contrast and brightness may be changed but only if it is done equally across a whole image and doesn’t lead to the removal of bands, spots or the background.

Answer 35

True

Question 36

When showing a blot in a paper, it is best to cut out the region with the bands of interest to make it easier for the editor and reviewers to read through.

Answer 36

False

Question 37

You don’t need to acknowledge that an image has been cut and joined as long as the join is neat and not noticeable.

Answer 37

False