Understanding Seasonality in Time-Series Analysis

In the context of time-series analysis, seasonality refers to periodic fluctuations in a data series that occur at regular intervals due to seasonal factors. An analyst is looking at quarterly sales data for a retail company over five years. They aim to understand the seasonal patterns in sales to better forecast future performance.

Given that the sales data exhibits a consistent pattern, where sales typically increase in the holiday season (Q4) and decrease during the summer months (Q2), which of the following statements best describes seasonality in this context?