## MA216-7-SP-CO:

Survival Analysis

## Key module for

MSC GN1312 Mathematics and Finance,

MSC GN1324 Mathematics and Finance,

DIP G30009 Statistics,

MSC G30012 Statistics,

DIP N32309 Actuarial Science,

MSC N32312 Actuarial Science,

MSC N32324 Actuarial Science,

MPHDG30048 Statistics,

PHD G30048 Statistics,

MPHDN32348 Actuarial Science,

PHD N32348 Actuarial Science

## Module description

Calculations in clinical trials, pensions and life and health insurance require reliable estimates of transition intensities/survival rates. This Survival Analysis module covers the estimation of these intensities.

The module also covers estimation procedures for lifetime distributions including censoring, Kaplan-Meier estimate, Nelson-Aalen estimate and Cox model; statistical models of transfers between multiple states; maximum likelihood estimators for the transition intensities; Binomial and Poisson models of mortality; estimation of age-dependent transition intensities; the graduation process; testing of graduations and measuring the exposed-to-risk.

## Module aims

The aims of this module are:

- to critically outline the distinctive characteristics of non-parametric estimation procedures for the lifetime distribution;
- to critically analyse and derive maximum likelihood estimators for the transition intensities;
- to examine in detail the Binomial and Poisson models of mortality and compare with the Markov models;
- to analytically describe the estimation procedure for transition intensities depending on age;
- to critically analyse and carry out tests for the consistency of crude estimates with a standard table or a set of graduated estimates;
- to describe in detail the process of graduation and the advantages and disadvantages of the various methods.
- to understand copula in bivariate survival models.
- to implement survival analysis models (e.g. Cox regression models and parametric regression models) using R

## Module learning outcomes

By the end of the module, students will be expected to be able to:

- Describe the principles of actuarial modelling
- Describe non-parametric estimation procedures for the lifetime distribution, including censoring, the Kaplan-Meier estimate, Nelson-Aalen estimate and Cox regression model (proportional hazards model);
- Describe parametric modelling approaches, specifically the parametric proportional hazards regression models and the Accelerated Failure Time (AFT) models.
- Derive maximum likelihood estimators (and hence estimates) for the transition intensities in models of transfers between states with piecewise constant transition intensities;
- Describe the Binomial and Poisson models of mortality, deriving maximum likelihood estimators for the probability/force of mortality and compare with the Markov models;
- Describe how to estimate transition intensities depending on age, exactly or using the census approximation, including calculation of exposed to risk and specification of census formulae based on various age definitions;
- Describe and carry out tests for the consistency of crude estimates with a standard table or a set of graduated estimates;
- Describe the process of graduation and the advantages and disadvantages of the various methods.
- Estimate and use survival analysis models with R

## Module information

This module covers the related units of CS2 (Risk Modelling and Survival Analysis, Core Principles), Institute and Faculty of Actuaries CS2 syllabus.

The syllabus includes the following: Concepts underlying actuarial modelling; distribution and density functions of the random future lifetime, the survival function and the force of hazard.

*Indicative syllabus:*

1. Concepts of actuarial modelling [CS2-4.1]: Describe why and how models are used, their benefits and limitations. Explain the concept of survival models. Describe the model of lifetime or failure time from age x as a random variable. State the consistency condition between the random variable representing lifetimes from different ages. Define the distribution and density functions of the random future lifetime, the survival function, the force of mortality or hazard rate, and derive relationships between them. State the Gompertz and Makeham laws of mortality. Compute life tables. Define the expected value and variance of the complete and curtate future lifetime and derive expressions for them. Define the curtate future lifetime from age x and state its probability function.

2. Exact or approximate estimations of transition intensities [CS2-4.4]: Describe the principle of correspondence and explain its fundamental importance in the estimation procedure. Specify the data needed for the exact calculation of a central exposed to risk (waiting time) depending on age and sex, and calculate a central exposed to risk. Explain how to obtain estimates of transition probabilities, including in the single decrement model and the actuarial estimate based on the simple adjustment to the central exposed to risk. Explain the assumptions underlying the census approximation of waiting times. Explain the concept of rate interval.

3. Explain the concept of survival models [CS2-4.2]: Recognise the characteristics of survival data, e.g. censoring and truncation Describe the various ways in which lifetime data might be censored Describe the Kaplan-Meier (or product limit) estimate of the survival function and the Nelson-Aalen estimate of the cumulative hazard rate; compute it from typical data and estimate its variance Determine the proper method to be used in analysing time-to-event data (e.g. parametric, semi-parametric or non-parametric method) Describe the Cox proportional hazard model, derive the partial likelihood estimate, and state its asymptotic distribution Perform survival analysis using a computer statistical software package, and interpret computer outputs.

4. Method of graduation and statistical tests [CS2-4.5]: Describe and apply statistical tests of the comparison of crude estimates with a standard mortality table testing for: a. the overall fit b. the presence of consistent bias c. the presence of individual age where the fit is poor d. the consistency of the 'shape' of the crude estimates and the standard table For each test describe: a. the formulation of the hypothesis b. the test statistic c. the distribution of the test statistic using approximations where appropriate d. the application of the test statistic e. how tests should be amended to compare crude and graduated sets of estimates f. how tests should be amended to allow for the presence of duplicate policies Describe the reasons for graduating crude estimates of transition intensities or probabilities and state the desirable properties of a set of graduated estimates

5. Mortality projection [CS2-4.6]: Describe the approaches to the forecasting of future mortality rates based on extrapolation, explanation and expectation, and their advantages and disadvantages. Describe the Lee-Carter, age-period-cohort, and p-spline regression models for forecasting mortality Use an appropriate computer package to apply the Lee-Carter, age-period-cohort, and p-spline regression models to a suitable mortality dataset. List the main sources of error in mortality forecasts.

6. Explain the basics of bivariate survival models (copulas) [CS2-1.3]: Explain that bivariate survival data are usually modelled via copulas. Describe how a copula can be characterised as a multivariate distribution function which is a function of the marginal distribution functions of its variates and explain how this allows the marginal distributions to be investigated separately form the dependency between them. Explain the meaning of the terms: dependence or concordance, upper and lower tail dependence; and state in general terms how tail dependence can be used to help select a copula suitable for modelling particular types of risk. Describe the form and characteristics of different types of copulas.

7. Introduction to extreme value theory [CS2-1.4]: Recognise extreme value distributions, suitable for modelling the distribution of severity of loss and their relationships. Calculate various measures of tail weight and interpret the results to compare the tail weights.

## Learning and teaching methods

Teaching in the School will be delivered using a range of face-to-face lectures, classes, and lab sessions as appropriate for each module. Modules may also include online only sessions where it is advantageous, for example for pedagogical reasons, to do so.

## Bibliography

## Assessment items, weightings and deadlines

Coursework / exam | Description | Deadline | Coursework weighting |
---|---|---|---|

Coursework | Test | ||

Exam | Main exam: In-Person, Open Book (Restricted), 180 minutes during Summer (Main Period) | ||

Exam | Reassessment Main exam: In-Person, Open Book (Restricted), 180 minutes during September (Reassessment Period) |

### Exam format definitions

**Remote, open book:**Your exam will take place remotely via an online learning platform. You may refer to any physical or electronic materials during the exam.**In-person, open book:**Your exam will take place on campus under invigilation. You may refer to any physical materials such as paper study notes or a textbook during the exam. Electronic devices may not be used in the exam.**In-person, open book (restricted):**The exam will take place on campus under invigilation. You may refer only to specific physical materials such as a named textbook during the exam. Permitted materials will be specified by your department. Electronic devices may not be used in the exam.**In-person, closed book:**The exam will take place on campus under invigilation. You may not refer to any physical materials or electronic devices during the exam. There may be times when a paper dictionary, for example, may be permitted in an otherwise closed book exam. Any exceptions will be specified by your department.

Your department will provide further guidance before your exams.

### Overall assessment

Coursework | Exam |
---|---|

30% | 70% |

### Reassessment

Coursework | Exam |
---|---|

30% | 70% |

## External examiner

**37**hours,

**37 (100%)**hours available to students:

**0**hours not recorded due to service coverage or fault;

**0**hours not recorded due to opt-out by lecturer(s).

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