Update docs/sphinx/source/index.rst

Co-authored-by: Martin Springer <97482055+martin-springer@users.noreply.github.com>

docs/sphinx/source/index.rst

@@ -53,7 +53,7 @@ The preferred method for degradation rate estimation is the year-on-year
 (YOY) approach (Jordan 2018), available in :py:func:`.degradation.degradation_year_on_year`.
 The YOY calculation yields a distribution of degradation rates, the
 central tendency of which is the most representative of the true
-degradation. We note that the workflow described above and implimented in 
+degradation. We note that the workflow described above and implemented in 
 :py:class:`.analysis_chains.TrendAnalysis` provides an estimate of degradation rate,
 not performance loss rate (PLR). PLR includes losses that are explicitly filtered
 out by the primary workflow (Deceglie 2023).