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HUNT 242 > Lecture 7 - Validity, Accuracy and Sensitivity > Flashcards

Lecture 7 - Validity, Accuracy and Sensitivity Flashcards

1
Q

what is validity

A

the extent to which a method gives you the correct answer

i.e measures what you want it to measure

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2
Q

what is absolute validity

A

reference method requires surreptitious measurement of intake

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3
Q

what is relative validity

A

reference method is another indirect method of assessing intake

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4
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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5
Q

what is repeatability also known as

A

reproducibility, reliability and precision

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6
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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7
Q

accuracy is not a word commonly used in nutrition, but what is it

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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8
Q

what is measurement error

A

difference between the measured value and the true value

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9
Q

observed intake is equal to

A

true intake + measurement error

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10
Q

what are the two types of measurement error

A

random error and systematic error

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11
Q

measurement error leads to

A
  • attenuation of relationships
  • bias
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12
Q

random error is due to

A

chance or normal variation

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13
Q

does random error change the mean

A

no it doesnt

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14
Q

random error increases….., therefore

A

variability around the mean, therefore decreased repeatability

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15
Q

what are the main sources of random error

A
  • daily variation in consumption
  • inaccurate portion size estimation
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16
Q

can random error be removed

A

not totally

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17
Q

systematic error is far more

A

concerning than random error

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18
Q

systematic error causes

A

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

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19
Q

systematic error changes ……, therefore

A

changes the mean, therefore decreased validity

20
Q

what are the main types of systematic error

A
  • selection bias (non-representative sample)
  • measurement bias (incorrect calibration)
21
Q

can systematic error be removed

A

can’t be removed by statistical analysis

22
Q

what is non response bias

A

people dont volunteer to participate

people dont adhere to intervention

people drop out

23
Q

in non response bias, a non representative sample may

A

may under or over estimate effects

24
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
25
Q

what is respondent bias

A

bias introduced by the respondent

26
Q

what are the three main types of respondent bias

A
  • low energy reporting
  • over reporting
  • social desirability and approval bias
27
Q

what are the strategies to minimise respondent bias

A
  • pre test methods
  • interviewer training
  • private interviews
  • identify flawed data
  • identify participants at risk
28
Q

what is interviewer bias

A

bias introduced by the interviewer

29
Q

interviewer bias may be caused by

A

incorrect recording

intentional omissions

poor cultural sensitivity

30
Q

what are the strategies to minimise interviewer bias

A

standardised computer interviews

train interviewers

identify problem interviewers

31
Q

what are the two forms of respondent memory lapses

A

errors of omission or errors of commission

32
Q

what are errors of omission

A

like when you forget something you ate

33
Q

what are errors of comission

A

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

34
Q

respondent memory lapses may be more likely …

A
  • longer time period to be recalled
  • men
  • age extremes
  • distracting environments
35
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

36
Q

incorrect portion estimate is probably

A

the largest source or error

37
Q

incorrect portion estimation is when they fail to

A

accurately quantify amount eaten

38
Q

incorrect portion estimation impacts

A

all ages, BMI, SES and genders

39
Q

what are the strategies to minmising incorrect portion estimation

A
  • measurement aids
  • train interviewers
  • train respondents
40
Q

what is the definition of supplements

A

there is no uniform definition of supplements

41
Q

omission of supplements leads to

A
  • systematic underestimation of nutrient intake
  • overestimation of prevalence inadequacy
42
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

43
Q

what is sensitivity

A

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

44
Q

what is specificity

A

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

45
Q

how to calculate sensitivity

A

TruePositives/ FalseNegatives(FN) + TruePositives(TP) ×100

46
Q

how to calculate specificity

A

True Negatives / True Negatives + False Positives x 100

47
Q

list the 9 errors in dietary assessment

A

non response bias

respondent bias

interviewer bias

respondent memory lapses

incorrect portion size estimation

omission of supplements

coding errors

errors in the handling of mixed dishes

errors in food composition databases

HUNT 242 (23 decks)

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