• Plotting in R
• Linear regression properly fitted or not
  • Residue are important thing to observed
  • Q-Q plots for normality test
  • Residues over time
    • Zoomed in residues over time
• Hypothesis test
  • One, two sided t test
  • Confidence interval
    • Where we think mean lies
    • If it dose not contain 0 we tend to reject null hypothesis (Very broad statement, but I think you got the concept)
• Correlation function
  • Which quarter data false

Ref : https://www.coursera.org/learn/practical-time-series-analysis/home/welcome