Fix typo on Act as a Statistician

[LeeDDHH]

Add New Prompt

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your prompt includes quotes, you will need to double-quote them to escape in CSV
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• I've confirmed the prompt works well
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  Contributed by: [@yourusername](https://github.com/yourusername)
• I've added to the README.md
• I've added to the prompts.csv
  • Escaped quotes by double-quoting them
  • No spaces after commas after double quotes. e.g. "Hello","hi", not
    "Hello", "hi"
  • Removed "Act as" from the title on CSV

Please make sure you've completed all the checklist.

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Description:
This pull request corrects one typographical errors in the README.md and prompt.csv:

Changed "probabillity" to "probability"