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The flight 19 departure delay times are depicted on a normal quantile plot.

The green straight line is depicted in the graph along with the dots, which represent the observation of departure delay times for flight 19.

The quartile plot represents the z-scores versus observations.

The inference from the quartile plot:

• If the observations follow a straight line pattern, the observations are inferred to be taken from a normal population.
• If the observations do not follow a straight line or follow a curvilinear pattern, the observations are inferred not to be taken from a normal population.

As the observations do not follow close to straight-line patterns, it can be inferred the observations are not taken from a normal distribution.

Also, as one observation lies to the extreme end, it can be determined that there exists an outlier in the data set.