Direct and Indirect standardisation.

Question 1

If a rate is described as ‘crude’ what has not happened to it?

Answer 1

It has not been adjusted.

Question 2

What makes it difficult to compare crude rates of mortality between populations?

Answer 2

Factors related to mortality may be distributed differently between the two populations.

Question 3

Apart from standardisation how can you compare two crude rates that have different distributions of underlining factors?

Answer 3

Comparison of stratum specific rates.

Question 4

What are the steps of direct standardisation (3 steps) ?

Answer 4

1. Select a standard population.
2. Obtain the proportion of person-time (or people) in each stratrum of the selected standard population.
3. Compute a weighted average of the stratum–specific measures in each population in order to combine stratum specific rates into a single measure.

Question 5

In order to carry out direct standardisation what do you need to know about the standard and studies population?

Answer 5

1. The distribution of the variable in the standard population.
2. Stratum specific rates of the study populations.

Question 6

The sum of what produces the incidence rate (in direct standardisation)?

Answer 6

(Rate in stratum l in population P)(Proportion of person time in stratum l in the standard population S). Sum for all stratums.

Question 7

The sum of what produces the incidence proportion/risk (in direct standardisation)?

Answer 7

(Risk in stratum l in population P)(Proportion of person time in stratum l in the standard population S). Sum for all stratums.

Question 8

Why do you not need to state a confidence interval in a standardised rate calculation?

Answer 8

As all the data has been included.

Question 9

Although in theory any population can be used in direct standardisation, what population(s) should you use?

Answer 9

Standard populations that include all study populations.

Question 10

Where can you obtain artificially created populations to use for direct standardisation?

Answer 10

WHO.

Question 11

What is the standard mortality ratio?

Answer 11

SMR= Observed events/ Expected events (if the study population had the same rates as the standard)

Question 12

What do you need to know to carry out indirect standardisation?

Answer 12

1. Known stratum specific rates in the standard population.

2. Known distribution of the variable in the study populations.

Question 13

What does a SMR of 1 mean?

Answer 13

There is no difference in observed events/expected events between the standard population and study populations.

Question 14

What does a SMR of >1 mean?

Answer 14

Less events in the study population than expected.

Question 15

What does a SMR<1 mean?

Answer 15

More events in the study population than expected.

Question 16

When would you use indirect standardisation over direct standardisation?

Answer 16

When the number of events are low.

Question 17

Does direct or indirect standardisation apply the stratum specific rates to the study population from the standard population?

Answer 17

Indirect.

Question 18

Does direct or indirect standardisation apply the stratum specific rates to the standard population from the study population?

Answer 18

Direct.

Question 19

What can you not investigate with standardisation?

Answer 19

The factor you have standardised for.

Question 20

Standard rates are summary measures. This can mask what in your data?

Answer 20

Trends/ differences in stratum specific rates which could be interesting.

Question 21

What type of standardisation allows for multiple comparisons to be made?

Answer 21

Direct.

Question 22

Do you need to know the overall crude rate of the entire population in direct standardisation?

Answer 22

No. This is an advantage of direct standardisation.

Question 23

What are two disadvantages of direct standardisation?

Answer 23

1. Changing the standard population might change the conclusion made.
2. High numbers of events required for stable age-specific rates.

Question 24

You do not need to know the overall crude rate in direct standardisation, however you do in indirect standardisation. What do you not need to know in indirect standardisation?

Answer 24

Stratum specific counts in standard population.

Question 25

Can indirect or direct standardisation be estimated with poisson regression?

Answer 25

Indirect.

Question 26

Why is indirect standardisation preferable when populations are small?

Answer 26

Greater precision than direct standardisation. Lower counts can result in unstable estimates.

Question 27

Is it easier to compare SMR’s with direct or indirect standardisation?

Answer 27

Direct.

Question 28

When are standardised rates useful?

Answer 28

When you want to make comparisons between populations or across time periods.

Question 29

Why can using the same standard populations consecutively over many years be problematic?

Answer 29

The standard populations may change over time which would result in the different rates.

Question 30

Standard populations should represent all study populations equally. True or False?

Answer 30

False. It can represent them differently as long as it makes sense.