Time series, normal distribution?

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SUMMARY

The discussion centers on the properties of a time series model defined by the equations x_1 = my + epsilon_1 and x_i = my + a(x_{i-1} - my) + epsilon_i, where epsilon_i are independent and identically distributed (iid) standard normal variables. It concludes that while each x_i is normally distributed due to the influence of the iid epsilon terms, the x_i are not independent. However, it is established that any linear combination of jointly Gaussian variables remains Gaussian, confirming that the linear combination y = a_1 x_1 + a_2 x_2 + ... + a_n x_n is indeed multivariate normal.

PREREQUISITES
  • Understanding of time series models and their components
  • Knowledge of independent and identically distributed (iid) random variables
  • Familiarity with properties of Gaussian distributions
  • Basic linear algebra concepts related to linear combinations of random variables
NEXT STEPS
  • Explore the implications of the Central Limit Theorem on time series data
  • Learn about the properties of multivariate normal distributions
  • Study the impact of autocorrelation on time series analysis
  • Investigate methods for estimating parameters in time series models
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Statisticians, data scientists, and researchers working with time series analysis and modeling, particularly those interested in the properties of Gaussian distributions and their applications in predictive modeling.

MaxManus
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Homework Statement



If I have a time series model

x_1 = my + epsilon_1
x_i = my + a(x_{i-1} - my) + epsilon_i

epsilon_i are iid standard normal.

Can I then say that
y = a_1 x_1+a_2 x_2 + ... a_n x_n

is multi normal?



The Attempt at a Solution



All the x-es are normal since they are built up of previous epsilons thich are independent and normal.

But the x-es are not independent so can I then say that a linear combination of them is normal
 
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absolutely, any linear combinations of joint Gaussian plus whatever constant is still joint Gaussian (in your case, iid Gaussian is a special joint Gaussian)
 
Thanks for the help.
 

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