Life Expectancy - Life Tables

Question 1

What is a life table?

Answer 1

Tables that are based on the probability of dying between one age (or age group) & the next age (or age group).

Question 2

How does a period life table work?

Answer 2

Life expectancy is calculated using age specific mortality rates (ASMRs) of that particular period.

Question 3

How does a cohort life table work?

Answer 3

Life expectancy is calculated using ASMR that change over time as people age.

Question 4

What is the difference between full life tables and abridged life tables?

Answer 4

Abridged life tables use age groups whereas full life tables use single years of age.

Question 5

Why do we focus on the ‘Period Abridged Life Table’?

Answer 5

We assume a stationary population.

Question 6

What does nMx mean?

Answer 6

Age-specific death rate between ages x and x+n.

Question 7

What does lx mean?

Answer 7

Number of people alive at exact age x.

Question 8

What does nQx mean?

Answer 8

Probability of dying between exact ages x and x+n.

Question 9

What does nPx mean?

Answer 9

Probability of surviving from exact age x to exact age x+n.

Question 10

What does nDx mean?

Answer 10

Number of deaths between exact ages x and x+n.

Question 11

What does nLx mean?

Answer 11

Average number alive in the interval between exact ages x and x+n, OR number of person-years lived in the interval between exact ages x and x+n.

Question 12

What does Tx mean?

Answer 12

Total population aged x and over, OR total number of person years lived from exact age x.

Question 13

What does Ex mean?

Answer 13

Expectation of life at exact age x.

Question 14

What does x mean?

Answer 14

The age at the start of an interval.

Question 15

What does n mean?

Answer 15

The number of years in an interval.

Question 16

What does person-years mean?

Answer 16

Sum of the years population has lived during a fixed interval/whole life.

Question 17

What does a(x) mean?

Answer 17

Fraction of the age interval lived by those in the cohort
population who die in the interval.

Question 18

How do you calculate the age-specific death rate?

Answer 18

Number of deaths at age x divided by population at age x.

Question 19

How do you calculate nQx?

Answer 19

n(nMx) divided by ( 1+ n(1-ax)nMx))

Question 20

How do you calculate nPx?

Answer 20

nPx= 1 – nQx

Question 21

What does I(x+n) mean?

Answer 21

The number of people alive at the start of interval.

Question 22

How do you calculate I(x+n)?

Answer 22

No. alive at start of interval = No. alive at start of previous interval x Probability of surviving
I(x+n) = l(x) multiplied by nPx

Question 23

List the assumptions of a period life table.

Answer 23

• A ‘Stationary Population’
• Population growth is constant
• Constant age structure
• Closed to migration