Calculates mean between-word duration WITHIN collections.

        :param str prefix: Prefix for the key entry in self.measures.

        Calculates the mean time between the end of each word in the collection
        and the beginning of the next word.  Note that these times do not necessarily
        reflect pauses, as collection members could be separated by asides or other noises.

        Adds the following measures to the self.measures dictionary:
            - TIMING_(similarity_measure)_(collection_type)_within_collection_interval_duration_mean

def compute_within_collection_interval_duration(self, prefix):
        """Calculates mean between-word duration WITHIN collections.

        :param str prefix: Prefix for the key entry in self.measures.

        Calculates the mean time between the end of each word in the collection
        and the beginning of the next word.  Note that these times do not necessarily
        reflect pauses, as collection members could be separated by asides or other noises.

        Adds the following measures to the self.measures dictionary:
            - TIMING_(similarity_measure)_(collection_type)_within_collection_interval_duration_mean
        """

        interstices = []
        for cluster in self.collection_list:
            # Make sure cluster is not a singleton
            if len(cluster) > 1:
                for i in range(len(cluster)):
                    if i != len(cluster) - 1:
                        interstice = cluster[i+1].start_time - cluster[i].end_time
                        interstices.append(interstice)

        self.measures[prefix + 'within_collection_interval_duration_mean'] = get_mean(interstices) \
            if len(interstices) > 0 else 'NA'

        if not self.quiet:
            print "Mean within-" + self.current_similarity_measure + "-" + self.current_collection_type + \
                  " between-word duration:", self.measures[prefix + 'within_collection_interval_duration_mean']