CWRU Physicist Predicts That Probability Strongly Favors McGwire Or Griffey Breaking Maris' Record
CLEVELAND--Mark McGwire of the St. Louis Cardinals has a 97 percent chance of making baseball history by breaking the home run record with 70 homers this season, according to Case Western Reserve University physicist Robert Brown, an avid baseball fan. And Brown stresses that McGwire has a stab at surpassing baseball legend "Babe" Ruth's record of 60 home runs in 154 games.
Brown says barring health or stress problems, there is a strong probability that McGwire will break Roger Maris' 1961 record of 61 home runs in 162 games. Together with rival Ken Griffey Jr. of the Seattle Mariners, there's a 99 percent chance that at least one of them breaks record. At this point, Sammy Sosa of the Chicago Cubs has less than a 50 percent chance for the record, according to Brown.
The McGwire-Griffey-Sosa push for the record-breaker is reminiscent of the fan frenzy surrounding the rivalry of Maris and Mickey Mantle, as each of the New York Yankees tried to make history in 1961 by surpassing George "Babe" Ruth's long-standing record of 60 home runs in 154 games, set in 1927.
According to Brown, McGwire has a very good chance -- 92 percent -- of breaking Ruth's record within the old standard of 154 games for a season. In 1961, Maris had only 58 homers in game 154. Maris tied Ruth's record in game 158. In the final game of the season, Maris broke the record with his 61st homer.
Brown, assisted by CWRU research scientist Norman Cheng, calculated the prediction using a simple binomial statistical analysis. The analysis is based on the number of games McGwire has left to play after July 21.
Brown bases his predictions on the fact that McGwire, so far this season, has been hitting at a new level, with one home run for every 9.2 totals at bat. Suppose that McGwire continues his season rate of total at bats per game for the remaining 64 contests, at a rate of 4.26 hits per game. This would give him 251 remaining times up to the plate for the rest of the season.
"We might expect him to hit one home run for every 9.2 at bats. Combining that with the remaining 251 times up to the plate leads to 27 more home runs, giving him a total of 70," predicts Brown. All results are changed very little in analyses differing in treatment of walks, sacrifice flies, and getting hit by pitches.
He adds that the probability of McGwire hitting 18 more home runs or fewer -- and not breaking the home run record -- is less than 3 percent. Thus he has a 97 percent chance or better of breaking the record.
Griffey, who hit his 40th home run against the Padres on July 21, has a 75 percent probability. Brown predicts that Griffey can end the season with 65 home runs.
Brown does note that a crucial unknown factor lies in injuries and illness which can result in missed games. If McGwire misses a week of games, his chances fall to 92 percent. After a month away from the field, it will be a long shot, as the probability drops to 16 percent.
NOTE: Figures cited in this article are based on players' statistics through July 22. Contact Robert Brown for updated probability calculations.