Scott Alexander gave a 70% probability that Robert Mueller would not indict Donald Trump during 2018.

The claim is judged on whether the predicted event happened by 31 December 2018, and also on whether the 70% figure is correctly attributed. TRUE: his January 2018 predictions post lists 'Mueller does not indict Trump: 70%', and Robert Mueller did not indict Donald Trump at any time in 2018. MOSTLY TRUE: the outcome holds, but the stated probability or wording in the post differs slightly (for example 60% or 80%). MOSTLY FALSE: the outcome holds, but the prediction is not in his 2018 predictions or is materially misattributed. FALSE: Mueller indicted Trump in 2018.

Set before the research began.

1. E1 Mueller report Wikipedia · 18 April 2019

   “The investigation intentionally took an approach that could not result in a judgment that Trump committed a crime.”

2. E2 Why Mueller said he couldn’t indict Trump, explained Vox · 24 July 2019

   “In his report, Mueller did not ultimately charge the president.”

3. E3 Why Mueller said he couldn’t indict Trump, explained Vox · 24 July 2019

   “We, at the outset, determined that, when it came to the president’s culpability, we needed to go forward only after taking into account the OLC opinion that indicated that a sitting president cannot be indicted,”

Vox reports that Mueller did not ultimately charge the president (E3). Vox quotes Mueller as saying his office decided at the outset to take into account the OLC opinion that a sitting president cannot be indicted (E4). Wikipedia describes an approach that could not result in a judgment that Trump committed a crime (E2). Because Trump was never indicted in the investigation, no indictment happened in 2018, so the predicted outcome holds. None of the evidence reproduces the January 2018 predictions post, so the 70% figure is taken from the claim's own quote rather than checked against the post.