Lecture 7

Question 1

There will always be error in dietary assessments. The challenge is to …..

Answer 1

understand and estimate the error structure during analysis

Question 2

What is validity

Answer 2

The extent to which a method gives you the “correct” answer ie measures what you want it to measure.

Question 3

P1 and P2 of validity

Answer 3

P1- Analysing anthropometric data
P2- Anthropometry assignment

Question 4

What is absolute validity

Answer 4

reference method requires surreptitious measurement of intake

Question 5

what is relative validity

Answer 5

reference method is another indirect method of assessing intake

Question 6

what is repeatability

Answer 6

the extent to which a method gives you the same answer each time you use it

Question 7

what is repeatability also known as

Answer 7

reproducibility, reliability and precision

Question 8

what are the issues to consider in a FFQ validation study

Answer 8

appropriate reference method = that does not require memory
study sample = needs to be accurate of what you are wanting to asses
timeframe = reference and FFQ should be over same timeframe
methods of statistical analysis

Question 9

Accuracy

Answer 9

accuracy is best used in a restricted statistical sense to describe the extent to which the measurement is close to the true value,

it has an important effect on the validity of the study

Question 10

what is measurement error

Answer 10

difference between the measured value and the true value

Question 11

observed intake is equal to

Answer 11

true intake + measurement error

Question 12

what are the two types of measurement error

Answer 12

random error and systematic error

Question 13

measurement error leads to

Answer 13

attenuation of relationships
bias

Question 14

random error is due to

Answer 14

chance or normal variation

Question 15

does random error change the mean

Answer 15

no it doesnt

Question 16

random error increases….., therefore

Answer 16

variability around the mean, therefore decreased repeatability

Question 17

what are the main sources of random error

Answer 17

• daily variation in consumption
• inaccurate portion size estimation

Question 18

can random error be removed

Answer 18

not totally

Question 19

systematic error is far more

Answer 19

concerning than random error

Question 20

systematic error causes

Answer 20

results to depart from the true value in constant direction (bias)

Question 21

systematic error changes ……, therefore

Answer 21

changes the mean, therefore decreased validity

Question 22

what are the main types of systematic error

Answer 22

• selection bias (non-representative sample)
• measurement bias (incorrect calibration)

Question 23

can systematic error be removed

Answer 23

can’t be removed by statistical analysis

Question 24

what is non response bias

Answer 24

people dont volunteer to participate

people dont adhere to intervention

people drop out

Question 25

in non response bias, a non representative sample may

Answer 25

may under or over estimate effects

Question 26

what are the strategies to minimise non response bias

Answer 26

- minimise response burden - mail or phone reminders - offer material rewards - train interviewers so warm and trusted - identify non responders and characterise - over sample groups at risk of non-responding

Question 27

what is respondent bias

Answer 27

bias introduced by the respondent

Question 28

what are the three main types of respondent bias

Answer 28

- low energy reporting - over reporting - social desirability and approval bias

Question 29

what are the strategies to minimise respondent bias

Answer 29

- pre test methods - interviewer training - private interviews - identify flawed data - identify participants at risk

Question 30

what is interviewer bias

Answer 30

bias introduced by the interviewer

Question 31

interviewer bias may be caused by

Answer 31

incorrect recording intentional omissions poor cultural sensitivity

Question 32

what are the strategies to minimise interviewer bias

Answer 32

standardised computer interviews train interviewers identify problem interviewers

Question 33

what are the two forms of respondent memory lapses

Answer 33

errors of omission errors of commision

Question 34

what are errors of omission

Answer 34

like when you forget something you ate

Question 35

what are errors of comission

Answer 35

can’t remember but will fill it in with something else

Question 36

respondent memory lapses may be more likely …

Answer 36

- longer time period to be recalled - men - age extremes - distracting environments

Question 37

what are strategies to avoid respondent memory lapses

Answer 37

multiple pass interviewing techniques - like when they have uninterrupted recall and then probing questions minimise time between intake and recall work with information retrieval

Question 38

incorrect portion estimate is probably

Answer 38

the largest source or error

Question 39

incorrect portion estimation is when they fail to

Answer 39

accurately quantify amount eaten

Question 40

incorrect portion estimation impacts

Answer 40

all ages, BMI, SES and genders

Question 41

what are the strategies to minmising incorrect portion estimation

Answer 41

- measurement aids - train interviewers - train respondents

Question 42

what is the definition of supplements

Answer 42

there is no uniform definition of supplements

Question 43

omission of supplements leads to

Answer 43

- systematic underestimation of nutrient intake - overestimation of prevalence inadequacy

Question 44

what are the strategies to minimising omission of supplements

Answer 44

structured questionnaire on long term intake closed ended questions on : brand, amount per unit, frequency of use, duration of use interviewer sights supplement

Question 45

what is sensitivity

Answer 45

how good the test / method is at correctly identifying people who have the disease / low status

Question 46

what is specificity

Answer 46

how good the test / method is at correctly identifying people who are well / have adequate status