(part A)

t.test(movie.jumps$IMDB.Rating,conf.level = 0.95)

One Sample t-test

data: movie.jumps$IMDB.Rating t = 98.082, df = 249, p-value < 2.2e-16 alternative hypothesis: true mean is not equal to 0 95 percent confidence interval: 5.765062 6.001338 sample estimates: mean of x 5.8832

(part B)

According to the given data, it is reasonable to conclude that the average IMDB rating of all horror movies lies somewhere within the range [5.765, 6.001].