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streaks

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  • John Grasso
    I ve recently being doing some research on the 1970-71 NBA season (individual high games - not streaks). This was the first year for the Buffalo, Cleveland
    Message 1 of 6 , Aug 17, 2001
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      I've recently being doing some research on the 1970-71 NBA season
      (individual high games - not streaks). This was the first year for the
      Buffalo, Cleveland and Portland franchises. Streaks seem to be quite
      prevalent. Here's a few examples.

      Cleveland - 15-67 for the season
      0-15 start
      1-0
      0-12
      1-0
      0-7
      1-0
      0-3
      2-0
      0-7
      6-4
      4-19 finish


      Detroit 12-1 start
      0-6
      11-7
      11-2
      11-21 finish
      45-37 season

      San Diego 23-20 start
      1-16
      8-2
      1-4
      7-0 finish (all home games)
      40-42 season

      Portland finished season
      5-0
      2-14
      5-0
      29-53 season
    • Dean Oliver
      ... the ... I just use the BINOMDIST() function in excel to calculate the probabilities of exceedences. It is pretty similar, if not the same to what MikeT
      Message 2 of 6 , Aug 17, 2001
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        --- In APBR_analysis@y..., "John Grasso" <johng@s...> wrote:
        > I've recently being doing some research on the 1970-71 NBA season
        > (individual high games - not streaks). This was the first year for
        the
        > Buffalo, Cleveland and Portland franchises. Streaks seem to be quite
        > prevalent. Here's a few examples.
        >

        I just use the BINOMDIST() function in excel to calculate the
        probabilities of exceedences. It is pretty similar, if not the same
        to what MikeT posted. I just haven't had a chance to carefully check
        it. (the 0.0014 number Mike calculated is actually almost the
        same as the 0.0017 number I calculated). Using the season records
        below as the "true" odds, I find the associated chances of these
        streaks occurring...

        > Cleveland - 15-67 for the season
        > 0-15 start (4.8%)
        > 1-0 (18.3%)
        > 0-12 (8.9%)
        > 1-0 (18.3%)
        > 0-7 (24.3%)
        > 1-0 (18.3%)
        > 0-3 (54.6%)
        > 2-0 (3.4%)
        > 0-7 (24.3%)
        > 6-4 (0.4%)
        > 4-19 finish
        >

        Only the 6-4 finish is that surprising. My sense, too, is that this
        kind of streak can definitely happen at the end of a bad season when
        no one cares about you.

        >
        > Detroit 12-1 start (0.5%)
        > 0-6 (0.8%)
        > 11-7 (38.7%)
        > 11-2 (2.6%)
        > 11-21 finish (1.6%)
        > 45-37 season
        >

        OK. These guys were streaky.

        > San Diego 23-20 start
        > 1-16 (0.02%)
        > 8-2 (4.7%)
        > 1-4 (20.3%)
        > 7-0 finish (all home games) (0.7%)
        > 40-42 season
        >

        2 pretty good streaks here, but, as you mention, we could do this more
        methodically and look at home/road numbers. If they were all home
        games, that would and the team won 60% of its home games (a pretty
        typical NBA figure for a 0.500 team), that moves the odds of a 7-0
        finish to 3.1%.

        > Portland finished season
        > 5-0 (0.6%)
        > 2-14 (4.2%)
        > 5-0 (0.6%)
        > 29-53 season

        The 5-0 streaks are weird.

        Dean Oliver
        Journal of Basketball Studies
      • John Grasso
        ... The 6-4 wasn t quite at the end of the season - after that hot streak they went 4-19 to finish the season - still they won 10 of their 15 victories in
        Message 3 of 6 , Aug 17, 2001
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          > > Cleveland - 0-15 start (4.8%)
          > > 1-0 (18.3%)
          > > 0-12 (8.9%)
          > > 1-0 (18.3%)
          > > 0-7 (24.3%)
          > > 1-0 (18.3%)
          > > 0-3 (54.6%)
          > > 2-0 (3.4%)
          > > 0-7 (24.3%)
          > > 6-4 (0.4%)
          > > 4-19
          > > 15-67 season
          >
          > Only the 6-4 finish is that surprising. My sense, too, is that this
          > kind of streak can definitely happen at the end of a bad season when
          > no one cares about you.

          The 6-4 wasn't quite at the end of the season - after that hot streak they
          went 4-19 to finish the season - still they won 10 of their 15 victories in
          their last 33 games. After the first 40 games they had only won 3 games and
          those were against the other two expansion teams. Their first win against an
          established team was over Philadelphia around Christmas.
        • Dean Oliver
          ... Something I realized about this analysis is that there are a lot of _possible_ streaks in a season. Though the 7-0 streak at the end had a 0.7% chance of
          Message 4 of 6 , Aug 17, 2001
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            --- In APBR_analysis@y..., "John Grasso" <johng@s...> wrote:
            > I've recently being doing some research on the 1970-71 NBA season
            >
            > San Diego 23-20 start
            > 1-16
            > 8-2
            > 1-4
            > 7-0 finish (all home games)
            > 40-42 season

            Something I realized about this analysis is that there are a lot of
            _possible_ streaks in a season. Though the 7-0 streak at the end had
            a 0.7% chance of happening, there were 75 possible sequences of 7
            games for this to happen in the season. Hence, the odds of this kind
            of team having 1+ series of 7 consecutive wins in a season are 39%.
            No big deal.

            On the other hand, the 1-16 streak was pretty strong. A 40-42 team
            has a 0.02% chance of going 1-16 in 17 games. There are about 55
            possible 17 game streaks in an 82 game season. The odds of any 40-42
            team having this kind of streak in an 82 game season are 1.1%. That
            is pretty impressive.

            Back to the Sting. They have a shorter season, only 32 games. The
            odds of having 1+ streak of 1-10 is 3.5% -- pretty unusual. The odds
            of having a 17-4 streak or better is 17%, not a big deal. Multiplying
            again (gulp), this makes for a 0.60% chance of such a season.

            Dean Oliver
            Journal of Basketball Studies
          • Charles Steinhardt
            I really need to dig up that paper... :)
            Message 5 of 6 , Aug 17, 2001
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              I really need to dig up that paper... :)

              On Fri, 17 Aug 2001, Dean Oliver wrote:

              > --- In APBR_analysis@y..., "John Grasso" <johng@s...> wrote:
              > > I've recently being doing some research on the 1970-71 NBA season
              > >
              > > San Diego 23-20 start
              > > 1-16
              > > 8-2
              > > 1-4
              > > 7-0 finish (all home games)
              > > 40-42 season
              >
              > Something I realized about this analysis is that there are a lot of
              > _possible_ streaks in a season. Though the 7-0 streak at the end had
              > a 0.7% chance of happening, there were 75 possible sequences of 7
              > games for this to happen in the season. Hence, the odds of this kind
              > of team having 1+ series of 7 consecutive wins in a season are 39%.
              > No big deal.
              >
              > On the other hand, the 1-16 streak was pretty strong. A 40-42 team
              > has a 0.02% chance of going 1-16 in 17 games. There are about 55
              > possible 17 game streaks in an 82 game season. The odds of any 40-42
              > team having this kind of streak in an 82 game season are 1.1%. That
              > is pretty impressive.
              >
              > Back to the Sting. They have a shorter season, only 32 games. The
              > odds of having 1+ streak of 1-10 is 3.5% -- pretty unusual. The odds
              > of having a 17-4 streak or better is 17%, not a big deal. Multiplying
              > again (gulp), this makes for a 0.60% chance of such a season.
              >
              > Dean Oliver
              > Journal of Basketball Studies
              >
              >
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            • Dean Oliver
              ... Given the extra work I did to evaluate the odds of a x% team having a streak of a certain type, I figured I d go back to this post and post the actual odds
              Message 6 of 6 , Aug 29, 2001
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                --- In APBR_analysis@y..., "John Grasso" <johng@s...> wrote:

                Given the extra work I did to evaluate the odds of a x% team having a
                streak of a certain type, I figured I'd go back to this post and post
                the actual odds of such a streak occurring. Low values, less than 5%,
                are considered pretty unusual.

                >
                > Cleveland - 15-67 for the season
                > 0-15 start (96.6%)
                > 1-0 (100%)
                > 0-12 (99.9%)
                > 1-0
                > 0-7
                > 1-0
                > 0-3
                > 2-0
                > 0-7
                > 6-4 (25%)
                > 4-19 finish
                >

                Nothing statistically unusual here. Even the 6-4 streak isn't that
                unusual for such a team.

                >
                > Detroit 12-1 start (29%)
                > 0-6 (48%)
                > 11-7
                > 11-2
                > 11-21 finish (55%)
                > 45-37 season
                >

                Nothing weird here either.

                > San Diego 23-20 start
                > 1-16 (1.3%)
                > 8-2
                > 1-4
                > 7-0 finish (all home games) (39%)
                > 40-42 season
                >

                The 1-16 run was weird. Everything else is normal.

                > Portland finished season
                > 5-0 (35%)
                > 2-14 (94%)
                > 5-0 (35%)
                > 29-53 season

                The odds of having 2 5-0 streaks is only 7%, so that may be a little
                weird. Otherwise, nothing statistically unusual.

                This really points out the old Tversky research that the mind
                perceives streaks a lot faster than stats would suggest they are
                really happening. Basically, if your mediocre team wins 5 or 7 in a
                row, it may not mean anything. It happens a lot to mediocre teams, as
                John pointed out here.

                I even ran the numbers on the 69-13 Lakers that won 33 straight. The
                likelihood of a random 69-13 team winning 33 straight is 15%, not that
                unusual for such a good team. It was more unusual to have a team that
                good throughout the season. This basically proves that the
                Lakers didn't win 69 by fluke. A 60-22 team wins 33 straight only
                0.17% of the time. A 65-17 teams wins 33 straight only in 2.3% of
                their seasons. What was the Bulls longest streak in their 72 win
                season? (Interestingly, I calculate that they had about a 50% chance
                of having a run of 33-0 in that season.)

                Dean Oliver
                Journal of Basketball Studies
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