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HUNT242 > Lecture 7 > Flashcards

Lecture 7 Flashcards

Validity, accuracy, sensitivity and friends

1
Q

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

A

understand and estimate the error structure during analysis

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2
Q

What is validity

A

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

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3
Q

P1 and P2 of validity

A

P1- Analysing anthropometric data
P2- Anthropometry assignment

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4
Q

What is absolute validity

A

reference method requires surreptitious measurement of intake

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5
Q

what is relative validity

A

reference method is another indirect method of assessing intake

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6
Q

what is repeatability

A

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

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7
Q

what is repeatability also known as

A

reproducibility, reliability and precision

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8
Q

what are the issues to consider in a FFQ validation study

A

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

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9
Q

Accuracy

A

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

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10
Q

what is measurement error

A

difference between the measured value and the true value

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11
Q

observed intake is equal to

A

true intake + measurement error

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12
Q

what are the two types of measurement error

A

random error and systematic error

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13
Q

measurement error leads to

A

attenuation of relationships
bias

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14
Q

random error is due to

A

chance or normal variation

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15
Q

does random error change the mean

A

no it doesnt

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16
Q

random error increases….., therefore

A

variability around the mean, therefore decreased repeatability

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17
Q

what are the main sources of random error

A
  • daily variation in consumption
  • inaccurate portion size estimation
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18
Q

can random error be removed

A

not totally

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19
Q

systematic error is far more

A

concerning than random error

20
Q

systematic error causes

A

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

21
Q

systematic error changes ……, therefore

A

changes the mean, therefore decreased validity

22
Q

what are the main types of systematic error

A
  • selection bias (non-representative sample)
  • measurement bias (incorrect calibration)
23
Q

can systematic error be removed

A

can’t be removed by statistical analysis

24
Q

what is non response bias

A

people dont volunteer to participate

people dont adhere to intervention

people drop out

25
Q

in non response bias, a non representative sample may

A

may under or over estimate effects

26
Q

what are the strategies to minimise non response bias

A
  • 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
27
Q

what is respondent bias

A

bias introduced by the respondent

28
Q

what are the three main types of respondent bias

A
  • low energy reporting
  • over reporting
  • social desirability and approval bias
29
Q

what are the strategies to minimise respondent bias

A
  • pre test methods
  • interviewer training
  • private interviews
  • identify flawed data
  • identify participants at risk
30
Q

what is interviewer bias

A

bias introduced by the interviewer

31
Q

interviewer bias may be caused by

A

incorrect recording

intentional omissions

poor cultural sensitivity

32
Q

what are the strategies to minimise interviewer bias

A

standardised computer interviews

train interviewers

identify problem interviewers

33
Q

what are the two forms of respondent memory lapses

A

errors of omission
errors of commision

34
Q

what are errors of omission

A

like when you forget something you ate

35
Q

what are errors of comission

A

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

36
Q

respondent memory lapses may be more likely …

A
  • longer time period to be recalled
  • men
  • age extremes
  • distracting environments
37
Q

what are strategies to avoid respondent memory lapses

A

multiple pass interviewing techniques
- like when they have uninterrupted recall and then probing questions

minimise time between intake and recall

work with information retrieval

38
Q

incorrect portion estimate is probably

A

the largest source or error

39
Q

incorrect portion estimation is when they fail to

A

accurately quantify amount eaten

40
Q

incorrect portion estimation impacts

A

all ages, BMI, SES and genders

41
Q

what are the strategies to minmising incorrect portion estimation

A
  • measurement aids
  • train interviewers
  • train respondents
42
Q

what is the definition of supplements

A

there is no uniform definition of supplements

43
Q

omission of supplements leads to

A
  • systematic underestimation of nutrient intake
  • overestimation of prevalence inadequacy
44
Q

what are the strategies to minimising omission of supplements

A

structured questionnaire on long term intake

closed ended questions on : brand, amount per unit, frequency of use, duration of use

interviewer sights supplement

45
Q

what is sensitivity

A

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

46
Q

what is specificity

A

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

HUNT242 (23 decks)

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