Surveillance of Google search terms wouldn't be revealed unless someone told the suspects directly (which these bumbling police officers essentially did).
It is entirely plausible that searches for "pressure cookers" and backpacks are some of several factors used to flag suspects. There is almost certainly a mandate to prevent pressure cooker bombings. I would guess they allotted some resource budget to that task and then simply created search criteria that narrowed the set of cases into one that could be investigated using those resources. I am pretty certain they didn't make any calculations of posterior probabilities.
There aren't nearly enough samples to make any kind of meaningful statistical assessment of efficacy, even if you believed that that was the primary decision making tool of the security agencies.
Assuming the story is true the NSA or FBI probably flagged these individuals using a number of factors (search terms, "anti-government" writing, etc) but not enough to merit use of limited federal resources. Still they hit on several risk factors so local police are informed, they may have additional information about these people and have boots on the ground to keep on eye on them (if something did happen then NSA and FBI could wash their hands: "We told the local police, they did nothing"). The comparatively unsophisticated local police, partly motivated by the same fear of being responsible if something did happen, then ham-fisted the investigation.
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Surveillance of Google search terms wouldn't be revealed unless someone told the suspects directly (which these bumbling police officers essentially did).
It is entirely plausible that searches for "pressure cookers" and backpacks are some of several factors used to flag suspects. There is almost certainly a mandate to prevent pressure cooker bombings. I would guess they allotted some resource budget to that task and then simply created search criteria that narrowed the set of cases into one that could be investigated using those resources. I am pretty certain they didn't make any calculations of posterior probabilities. There aren't nearly enough samples to make any kind of meaningful statistical assessment of efficacy, even if you believed that that was the primary decision making tool of the security agencies.
Assuming the story is true the NSA or FBI probably flagged these individuals using a number of factors (search terms, "anti-government" writing, etc) but not enough to merit use of limited federal resources. Still they hit on several risk factors so local police are informed, they may have additional information about these people and have boots on the ground to keep on eye on them (if something did happen then NSA and FBI could wash their hands: "We told the local police, they did nothing"). The comparatively unsophisticated local police, partly motivated by the same fear of being responsible if something did happen, then ham-fisted the investigation.