I linked the study above. Note that the individual probability of intervention falls as the number of people goes up (and the study you cited mentions this).
In some situations, it looks like the total probability of any intervention goes up as the number of people increases. In other situations, it looks like it goes down. The paper cited to produce that couple of sentences on Wikipedia makes the distinction quite clear and does not dispute the individual probability of intervention falls: https://eprints.lancs.ac.uk/id/eprint/134891/1/Would_I_be_He...
Note that it quite clearly says that it does not refute the bystander effect: ". It is important that by examining intervention on the situational rather than
the individual level, our research does not evaluate whether bystanders are less likely to
provide help when in the presence of other bystanders compared with when they are alone
(i.e., the bystander effect). "
I agree and don't dispute the Kitty Genovese thing was bullshit, but the bystander effect-- a reduced probability for individuals to respond when more people are around-- is one of the most replicated findings in behavioral psychology.
As to the probability of someone intervening-- it looks like the odds are best when a small number of people are around vs. property crime, and best when a large number of people are around vs. dangerous/emergency situations. Also, the efficacy of the latter intervention, assessed by victims, seems to fall as the number of surrounding people increase.
This is all well discussed in the wikipedia article and in the text of the particular study you're relying upon.
I linked the study above. Note that the individual probability of intervention falls as the number of people goes up (and the study you cited mentions this).
In some situations, it looks like the total probability of any intervention goes up as the number of people increases. In other situations, it looks like it goes down. The paper cited to produce that couple of sentences on Wikipedia makes the distinction quite clear and does not dispute the individual probability of intervention falls: https://eprints.lancs.ac.uk/id/eprint/134891/1/Would_I_be_He...
Note that it quite clearly says that it does not refute the bystander effect: ". It is important that by examining intervention on the situational rather than the individual level, our research does not evaluate whether bystanders are less likely to provide help when in the presence of other bystanders compared with when they are alone (i.e., the bystander effect). "
I agree and don't dispute the Kitty Genovese thing was bullshit, but the bystander effect-- a reduced probability for individuals to respond when more people are around-- is one of the most replicated findings in behavioral psychology.
As to the probability of someone intervening-- it looks like the odds are best when a small number of people are around vs. property crime, and best when a large number of people are around vs. dangerous/emergency situations. Also, the efficacy of the latter intervention, assessed by victims, seems to fall as the number of surrounding people increase.
This is all well discussed in the wikipedia article and in the text of the particular study you're relying upon.