Portfolio Theory Flashcards
What is a portfolio?
A collection of securities with different risks and returns associated.
What is the realised return?
A geometric average of past returns.
What are the three characteristics of portfolios?
First: Expected Return
Second: Variance
Third: Covariance
What is the expected return?
Expected return is the best guess for the return that will be achieved the next period.
What are the methodologies we can use to find the expected return?
Distribution of Returns and Sample of Past Returns
What is the formula for the expected return when we use the methodology of distribution of returns?
E(ri) = ∑piri
What is the excel formula we should use to find the expected return (using distribution of returns)?
=sumproduct()
When can we use the mean return to find the expected return?
When observations are independent and identical distributed, the Law of Large Numbers states that the mean return converges in probability to the true expected return,
What is the excel formula we should use to find the expected return (using a sample of past returns)?
=average
What is the variance of the return?
The best guess for the measurement error. It tells us how much should an investor expect to fail prediction. It is the measure of risk.
What are the methodologies we can use to find the variance?
Distribution of Returns and Sample of Past Returns
What is the formula to find the variance using the distribution of returns?
∑ pi [ri - E(ri)]^2
True or false: The variance of the mean return is the true variance.
False
What is the volatitility?
The risk, it’s the standard deviation
In excel, what formula should we use to find the variance?
=var.s()
In excel, what formula should we use to find the standard deviation?
=stdev.s()
What does the covariance measure?
The relationship between two random variables.
What does it mean when a covariance is positive?
On expectation, the returns of the two securities move in the same direction.
What does it mean when a covariance is negative?
On expectation, the returns of the two securities move in opposite directions.
What does it mean when a covariance is zero?
We suspect the securities are independent.
Why do we compute the coefficient of correlation?
Because we can only interpret the sign of the covariance.
What is the interval of values the coefficient of correlation can take?
Between-1 to 1
How do you calculate the coefficient of correlation?
COV/σaσb
What does it mean if the coefficient of correlation is 1?
The two securities move by the same amount in % points in the same direction.
What does it mean if the coefficient of correlation is -1?
The two securities move by the same amount in % points in opposite directions.
In Excel, how do you compute the covariance?
=covariance.s()
In Excel, how do you compute the coefficient of correlation?
=correl()
How can risks be grouped?
Firm Specific/Idiosyncratic Risk and Systematic Risk
What is Idiosyncratic Risk?
Types of risk that share no correlation.
What is Systematic Risk?
Risk that affects all firms, but not all in the same way.
How do we compute the weight?
Value allocated in a specific security/Wealth
What is a long position?
When an investor invests in a security, the return will be received. w > 0
What is a short position?
When an investor short sells a security, the return will be paid.
w < 0
What is the expected return of a portfolio?
The weighted average of the expected return of its components.
True or false: when focusing on diversification, we focus on long positions and short positions.
False, only long positions
Why do investors create portfolio?
Gains from diversification
True or false: there is an added advantage of creating portfolios in terms of returns.
False, the expected return of a portfolio is given by the weighted average of the individual expected returns.
True or false: the portfolio’s volatility is the weighted average of the individual volatilities.
False, due to the covariance term.
What are the gains from diversification?
The difference between the portfolio’s volatility and the average volatility of the individual securities in the portfolio.
When do we have gains from diversification?
When the standard deviation of the portfolio is lower than the individual standard deviations.