This word is impossible to spell!!!!
One way is to remember is to break it down into the parts that make up the derivation. It is based on the word "effektiv", "-itet" is a common way to make nouns out of (especially Latin-based) words.
Hög doesn't take the definite ending -a because it follows the definite noun. But, den höga effektiviteten. ?
Why not ...är stor...high means large or great ?
In Dutch we make a difference between effectiviteit (how big is the effect?) and efficiency (is, regarding to the input, the effect quite big?). Is the Swedish "Effektivitet" used for both?
Yes, it is, and for that reason effekt is one of those words Swedes very frequently get wrong when translating into English.
Mmh, it is striking that effektivitet is en 'en' word and e.g. universitet is an 'ett' word, so apparently words with -et ending can be neuter or non-neuter.
Yup. In this case they've been borrowed from different source languages, so I imagine that's the reason.