Learn French: Les données sont bizarres, alors la conclusion est intéressante. - The data are bizarre, so the conclusion is interesting.

Yes! Both alors and donc express a consequence. Alors is like saying "so" and is very common in everyday speech. Donc is slightly more formal, like "therefore". In this sentence, either one works perfectly.

Why is it les données sont (plural) when English often uses "the data is" (singular)?

In French, une donnée means a single fact or piece of information. When talking about data in general, French always uses the plural form les données. Because the noun is plural, you must use the plural verb sont and make the adjective plural too (bizarres).

Why does bizarres end in an -s while intéressante doesn't?

Adjectives must match the noun they describe. Bizarres describes les données, which is plural, so it takes an -s. Intéressante describes la conclusion, which is singular, so it takes no -s. However, notice that intéressante gets an -e at the end because conclusion is feminine!

How can I remember that conclusion is a feminine noun?

A great rule of thumb is that almost all French nouns ending in -sion or -tion (like la conclusion, la station, or la question) are feminine.