Learn Italian: L'ipotesi è pronta, quindi dobbiamo misurare la temperatura. - The hypothesis is ready, therefore we must measure the temperature.

Yes, you could use perciò or dunque here! Quindi means "therefore" or "so" and connects a cause (the hypothesis being ready) to its logical consequence (needing to measure the temperature). They are all coordinating conjunctions of result and are mostly interchangeable in this context.

Why does ipotesi end in -i if it is a singular word?

Ipotesi is a feminine noun of Greek origin. In Italian, many nouns ending in -i (like la crisi or l'analisi) are feminine and do not change their spelling in the plural. You can tell it is singular here because it is paired with the singular verb è and the singular adjective pronta.

Does pronta end in -a because it describes ipotesi?

Exactly. Even though ipotesi ends in -i, it is a feminine singular noun. Therefore, the adjective pronta (ready) must take the feminine singular ending -a to agree with it.

Why is misurare left in its dictionary form?