FIEL DIARIES #15

Date: 10 - April- 2021

Topic: Time series

Objective: Analyze the variabilities of the time series such as: trend, cyclical fluctuations, seasonal variations and irregular variations by reviewing concepts for application in tourism.

Shared resources:

Informatics in Company

Brief summary of what was exposed in class:

Descriptive analysis of a time series

A time series is a sequence of data or observations, measured at certain times and arranged chronologically. Visually, it is a curve that evolves over time. A time series is a set of observations about the values ​​that a (quantitative) variable takes over time.

In general, the objective of descriptive statistics is to provide us with methods (both graphical and quantitative) that allow us to summarize and extract information from a set of observations taken from a variable.

Before a time series, the first thing to do is represent its sequence graph; that is, represent graphically each observation xt against the instant t at which it is observed, and then join each of the T points with segments.

The sequence graph will allow us to observe how it evolves the series over time; specifically, we will be able to see the main characteristics of the time series:

- Possible presence of trend: long-term behavior of the series.

- Possible presence of seasonality: periodic behavior of the series.

- Possible presence of heteroscedasticity: the variability of the series depends on its level.

Classical Decomposition of a Time Series

To build a model that describes in a simple way the evolution of the series through time. To do this, it is assumed that the xt data can be expressed as a function of a trend component Tt, a seasonal component St and an error at: Tt models the long-term behavior of the series. St models the periodic behavior of the series. at is formed by the effect of various factors of little importance that are often unknown to us. It represents the unpredictable part of the series.

Classification of time series

A series is stationary if the mean and variability hold constant over time.

A series is non-stationary if the mean and / or variability change over time.

Non-stationary series can show changes in variance.

Non-stationary series can show a trend, that is, the average grows or falls over time.

In addition, they can present seasonal effects, that is, the behavior of the series is similar at certain times newspapers in time.

Personal conclusions

In today's class they learned what a time series is, which is a time or chronological series, it is a succession of data measured at certain times and ordered chronologically. The data can be spaced at equal or unequal intervals.

Task:

Based on the INEC page (Click) search for 3 statistical results that contribute to tourism. Justify your choice.