W10 Statistics

Question 1

Calculating the mean, median & the mode

Answer 1

Mean- sum of all numbers and divide by number of numbers (average)
Median- Order numbers lowest to highest, middle number is median. If two, add both and divide by 2
Mode- Most common number

Question 2

Calculate the mean, median and mode of these numbers:
72 148 127 171 72

Answer 2

mode = 72
mean= 118
median: = 127 72 72 127 148 171

Question 3

Define:

Range
Variance
Standard deviation

Answer 3

• Range- distance between the smallest & largest result
• Variance- How far the numbers are spread around the mean
• Calc: calculate the difference between each point and the mean; then, square, sum and divide by the sample size less 1 ( mean of squares- square of mean)
• Standard deviation – a measure to use as a comparison. How far something deviates from the mean value.
• Calc: square root of the variance

Question 4

Why is standard deviation useful?

Answer 4

• Results that are within 1 standard deviation are much closer to the mean i.e. more “normal”.
• Allows us to compare results: SD of Data A < SD of Data B, then data in A is closer to the mean

Question 5

What is the general pattern for observations?

Answer 5

68%= values within 1 SD of the mean
95%= values within 2 SD of the mean
99.7%= values within 3 SD of the mean

Question 6

What is the Null and Alternative hypothesis?

Answer 6

Null hypothesis Ho: There is no difference in the
average change in LDL cholesterol based on the
statin received.
Alternative hypothesis H1: That Ho is false

Question 7

If we reject the null hypothesis when Ho is true=

If we fail to reject the null hypothesis when Ho is false=

Answer 7

1. Type l error
2. Type ll error

Question 8

Bias

Answer 8

• Publication bias is not necessarily scientific fraud
• a problem for clinical trials where pharmaceutical companies less likely to
  publish results that aren’t favourable
• Experimental bias
• simply measuring can be vulnerable to perception biases
• subtle omissions and unconscious misperceptions, as researchers struggle to
  make sense of their results or scientists find ways to confirm their preferred
  hypothesis, disregarding what they don’t want to see
• Research on the effectiveness of acupuncture (1966 and 1995):
• China, Taiwan, Japan 100%
• United States, Sweden, UK 56%

Question 9

Which variables are controlled and uncontrolled?
What do they measure?
(Independent and Dependent)

Answer 9

Independent variable- controlled (what you change)
Dependent variable- not controlled (what you measure)

Question 10

What is the shape of the curve in a normal distribution?

Answer 10

Bell-shaped